Balance Cock—The standard which supports the top pivot of the balance. In old watches often elaborately pierced and engraved.

Balance Spring—In America usually called the "hair-spring." A long slender spring that governs the time of vibration of the balance. One end of the balance spring is fastened to a collet fitted friction-tight on the balance staff, the other to a stud attached to the balance cock or to the watch plate. The most ordinary form is the volute, or flat spiral. The other form used is an overcoil. See BrÉquet Spring. The principle of the isochronism of a balance spring was discovered by Hooke, and first applied to a watch by Tompion. The name hair-spring comes from the fact that the first ones are said to have been made from hog bristles.

Balance Spring Buckle or "Guard"—A small stud with a projecting tongue attached to the index arm and bridging the curb pins so as to prevent their engaging two of the balance spring coils. Used chiefly in Swiss watches.

Balance Staff—The axis of the balance. The part of a watch most likely to be injured by a fall.

Balance Wheel—A term often incorrectly applied to the balance itself, but properly it is the escape wheel of the verge escapement.

Band—Of a Watchcase—The "middle" of the case to which the dome, bottom and bezel are fastened; the last sometimes screwed, sometimes snapped.

Bank—Banking-pin.

Banking—In a lever watch the striking of the outside of the lever by the impulse pin due to excessive vibration of the balance. In a cylinder or verge movement the striking of the pin in the balance against the fixed banking-pin.

Banking-Pin—A pin for restricting the motion of the balance in verge and cylinder watches.

Banking-Pins—1. In a lever watch, two pins which limit the motion of the lever. 2. In a pocket chronometer, two upright pins in the balance arm which limit the motion of the balance spring. 3. In any watch, the curb pins which confine the balance spring are sometimes called banking-pins.

Barlow, Edward (Booth)—A clergyman of the Church of England, born in 1636. He devoted a great deal of time to horological pursuits. He invented the rack repeating striking works for clocks, applied by Tompion in 1676. He invented also a repeating works for watches on the same plan. And he invented the cylinder escapement which he patented with Tompion and Houghton. When he applied for a patent on his repeating watch he was successfully contested by Quare, who was backed by the Clockmakers' Company. He died in 1716.

Bar Movement—A watch movement in which bars take the place of the top plate and carry the upper pivots. Sometimes termed a "skeleton" movement. Not generally adopted because its many separate bearing parts promote inaccuracies where large quantities are to be produced.

Barrel—A circular box which confines the mainspring of a watch or clock.

Barrel Arbor—The axis of the barrel around which the mainspring is coiled.

Barrel Hollow—A sink cut either into the top plate or the pillar plate of a watch to allow the barrel freedom.

Barrel Hook—A bent pin in the barrel to which the mainspring is attached.

Barrel Ratchet—A wheel on the barrel arbor which is prevented by a dog from turning backward while the mainspring is being wound and which becomes the base against whose resistance the train is driven.

Bartlett, P. S.—One of the early watchmakers of America. Connected with the Waltham factory at first and later with the Elgin Company. It is said that he first proposed the formation of the company at Elgin. His name became familiar as a household word throughout the country from being inscribed upon a full-plate model which attained widespread success.

Beat—The strike or blow of the escape wheel upon the pallet or locking device.

Beat Pins—The pins at the ends of the pallets in a gravity escapement which give impulse to the pendulum.

Beckett, Sir Edmund—See Denison, Edmund Beckett.

Berosus—A Chaldean historian who lived at the time of Alexander the Great, about 200 B. C., and was a priest of Belus at Babylon. Said to have been the inventor of the hollow sun-dial. He was the great astronomer of his age.

Berthoud, Ferdinand, 1727-1807— An eminent French watchmaker and writer on horological subjects. Among his books are: "Essai sur l'Horlogerie," "Traite des Horloges Marines," and "Histoire de la mesure du Temps." He was a Swiss by birth, but lived most of his life in Paris.

Bezel—The ring of a watch or clock case which carries the glass or crystal in an internal groove.

Big Ben—The great bell which strikes the hours on the clock at Westminster.

Bizzle—A corruption of Bezel. See Bezel.

Blow Holes—Places where the brass and steel of a compensation balance are not perfectly united, when they are put together with silver or solder.

Bob—The metal mass forming the body of a pendulum.

Boethius, Ancius Manlius Severinus, A. D. 480-524—A Roman philosopher and statesman to whom is sometimes attributed the invention of the clock. He did make a sun-dial and a water clock which latter may have contained a germ of the idea later developed into our modern clock.

Boss—A cylindrical prominence or stud. The minute hand is carried on the boss of the center wheel.

Bottom—Of a Watchcase—The cover outside the dome of the case. Commonly called the "back."

Bouchon—The hard brass tubing of which pivot holes in watch and clock plates are made; known commonly as "bushing wire." The short sections cut off for a pivot being called the "bushing."

Bow—The ring of a watch case to which the guard or chain is attached; also known as "pendant bow."

Box Chronometer—A marine chronometer.

Boxing-In—Fitting the watch movement in its case; applied chiefly to the encasing of stem-winding movements.

BrÉquet, Abraham Louis—A celebrated Swiss mechanician and watchmaker born at Neufchatel in 1747. He made several improvements in watches, the most notable being the BrÉquet hairspring still in use in the best watches. He died in 1823.

BrÉquet Spring—A form of balance spring which is a volute with its outer end bent up above the plane of the body of the spring and carried in a long curve towards the center near which it is fixed. Like all other springs in which the outer coil returns towards the center, it offers opportunities of obtaining isochronism by varying the character of the curves described by the outer coil and thus altering its resistance. So-called from its inventor, Abraham Louis BrÉquet (q. v.). Its advantage over the flat spring is that the overcoil allows expansion and contraction in all directions, thereby avoiding a good deal of side friction on the pivots as well as insuring more nearly perfect isochronism in changes of temperature.

Bridge—A standard fastened to the plate, in which a pivot works.

Bridge Model—The term given to watch movements in which plates or bridges carrying the upper pivots of the train rest firmly on the lower or dial plate and are held rigid by steady pins on lower side of the plate; the bridge being secured direct to the dial plate by screws termed plate or bridge screws. This is the most common construction of present-day manufacture and is utilized in three-quarter plate or separate and combination bridges covering one or more pivots of train wheels. Its alternate is "pillar model."

Buck, D. A. A.—A watch repairer in Worcester, Mass., who designed a model for the Waterbury watch. His first model was not successful, but in 1877 he completed one which, a little later, the Waterbury Company, with Buck as master watchmaker, started to make. He remained with the company until 1884.

Bush—A perforated piece of metal let into a plate to receive the wear of pivots.

Butting—The engaging of the tips of the teeth of two wheels acting in gear. The proper point of contact being in the line of the shoulders of the teeth, butting is remedied by setting the wheels farther apart.

Button—The milled knob used for winding and setting a keyless watch.

Calculagraph—Trade name for a device for automatically computing and recording elapsed time in connection with factory jobs and other work where it is necessary to show the amount of labor used.

Calendar—A system of dividing the year into months and days. The principal calendars known to history are: the Julian calendar; the Gregorian calendar; the Hebrew calendar; the Mohammedan calendar; and the Republican calendar. None of them has been quite accurate in dividing up the solar year, and frequent arbitrary corrections are necessary to secure a practical approximation. See descriptive article under each title.

Julian—Established by Julius Caesar, 46 B. C., to remedy existing defects in the Roman calendar then in use. The Julian year was based on the assumption that the solar year is 365¼ days—which was 11 minutes and 14 seconds too long. The scheme adopted was to make the regular calendar year 365 days, and to add one day every fourth year. The Julian calendar is still in use by Russia and Greece, where the dates now differ from those of most other countries by 13 days.

Gregorian—Established October 15, 1582, by Pope Gregory XIII, in correction of the obvious errors of the Julian calendar. It is the calendar now in use by nearly all civilized nations. The mean length of the Gregorian year is 365 days, 5 hours, 49 minutes and 12 seconds—26 seconds longer than the actual solar year. Correction is made by adding a 29th day for February every fourth year, excepting when the date of said fourth year is divisible by 100. If, however, the date is also divisible by 400, the extra day is added.

Republican—The calendar of the French Revolution (1793) declared to begin at midnight on the meridian of the Paris Observatory preceding the true autumnal equinox, September 22, 1792. There were 12 months of 30 days each and 5 or 6 "extra days" (as might be necessary) at the end of the year to bring the new year nearest to the then position of the equinox. Abolished January 1, 1806.

Hebrew—Composed of 12 lunar months, a thirteenth month being added from time to time to secure correspondence of the months with the passing seasons. The months are arbitrarily arranged to have alternately 29 days and 30 days. The length of the calendar year varies from 353 days to 385 days.

Mohammedan—Based on a lunar year of 354 days divided into 12 lunar months which are alternately 29 and 30 days in length. During each period of 30 years a total of 11 days are added one at a time at the end of a year. The lack of co-ordination with the solar year results in a total separation of the seasonal year and the calendar year. In use in Turkey and some other Mohammedan countries.

Calendar Clock, or Watch—A clock or watch which indicates days and months as well as hours.

Caliper—The scheme of arrangement of a watch train, or the disposition of the parts of a watch.

Cam—A rotating piece either non-circular or eccentric, used to convert rotary into linear reciprocating motion, oftener irregular in direction, rate, or time.

Cannon Pinion—The pinion to which the minute hand is attached. It is tubular in form (whence its name), the main arbor passing through it friction-tight.

Canton Berne—The Swiss district which does the largest export business in silver and base metal watches in Switzerland. The cantonal government has done everything possible to promote the industry, among other things: 1. Established information offices in the principal watch-making centers. 2. Established a permanent exhibition of articles used in the industry. 3. Established schools and associations and protective territories. 4. Prepared statistics and means for negotiating commercial relations.

Cap—The part of the case that covers the movement.

Capped Jewel—A jewel having a protective end-stone.

Carillon—Chimes frequently used in the earlier clocks for striking the hours. Still used in some clocks.

Caron, Peter Augustus—A famous Paris watchmaker, afterward called Beaumarchais, who made the first keyless watch of which we have any account.

Case—The metal box in which the movement of a watch is inclosed.

Case-Springs—The springs which cause the outer bottom of a watch case to fly open when the lock spring is released.

Center of Gyration—That point in which the whole mass of a rotating body might be concentrated without altering its moment of inertia.

Center of Oscillation—That point in a pendulum at which, if the whole mass of the pendulum were collected, the time of oscillation would be the same.

Center Seconds or Sweep Seconds—A long seconds hand moved from the center of a watch dial, as are the minute and hour hands.

Center Staff—The arbor attached to the center wheel which carries the minute hand.

Center Wheel—The wheel in ordinary clocks and watches placed in the center of the frame on whose arbor the minute hand is carried. It is intermediate between the barrel and the third wheel.

Chamfer—To cut away to a bevel the right angle formed by two adjacent faces as of a jewel or stone. It is also occasionally used to signify channeling or grooving.

Chasing—A form of ornament for metals which is made by punching or pressing from behind to present the pattern in relief instead of by cutting away the material.

Chops—In a pendulum clock the blocks, usually of brass, between which the top of the pendulum suspension spring is clipped to prevent its twisting as it swings.

Chronograph—In general, a recording clock or watch. Specifically, a watch with a center-seconds hand which may be stopped, started or returned to zero at will by pressing a button. Used for timing races, or measuring other short spaces of time with great exactness.

Chronometer—Any very accurate time-keeper. Usually understood to mean a time-keeper fitted with a spring detent escapement. They usually have a fusee and a cylindrical balance spring.

Chronometer, Marine—Probably the most exact form of time-keeper, especially for use on shipboard. The driving power is a mainspring acting by a chain on a fusee, and governed by what is known as the Chronometer or Detent Escapement, with, as a rule, the cylindrical balance spring. The movement is mounted on gimbals in an air and water-tight brass case, maintaining the dial constantly in a horizontal position.

Chronoscope—A clock or watch in which the time is shown by figures presented at openings in the dial.

Church, Duane H.—Credited with having contributed more to the automatic features of watch machinery than any other man. He was born in Madison County, N. Y., in 1849. At 16 he was apprenticed to a watchmaker of St. Paul, Minn., and after working at the trade for 17 years, he became in 1882 the master watchmaker for the Waltham Watch Company. Besides his invaluable contributions to automatic machinery, he improved the general design of watch movements and invented a form of pendant setting which enables stem-winding movements to be set in cases not especially adapted to them. He died in 1905.

Circular Error—The difference in time arising from the swinging of a pendulum in a circular arc instead of its true theoretical path which is a cycloidal arc. This caused much trouble in the early clocks. Huyghens attempted to correct it (see Huyghens' Checks) but found that his device caused greater error. With the heavier pendulum and shorter arcs of vibration this error becomes negligible. The suspension of the pendulum by a flat flexible spring instead of a cord, attributed to Dr. Hooke, served to make the path practically cycloidal.

Cleopatra's Needle—An Egyptian obelisk at whose base a dial was marked. Now in London. Another similar obelisk from Egypt is in Central Park, New York City.

Clepsammia—The sand-glass, more familiarly known as the hour-glass. See Hour-glass; Sand-glass.

Clepsydra—A device for the measurement of time by the flow of running water. Its simplest form is a vessel filled with water which trickles or drops slowly from a small aperture into another vessel. One or the other of the vessels is graduated and the height of the water in that one at any given time indicates the hour. Sometimes a figure floating on the water points to the hours. Later, falling, or running, water was made to turn wheels or to move a drum, as in "Vailly's clock." Clepsydras were made and improved up to the 17th century. The earliest known example—one in China—is credited with having existed in 4000 B. C. The name indicates the stealing away of water and is derived from two Greek words meaning "water" and "to steal." A common form of clepsydra in India was a copper bowl with a small hole in the bottom floating on water. When the bowl filled and sank the attendant emptied it, struck the hour upon it and floated it again on the surface of the water. Like the sun-dial, the clepsydra was invented so long ago that there is no authentic record of its origin. Its evident advantages are exactly those which the sun-dial lacked. It is quite independent of day or night or other external conditions; it is conveniently made portable; and by regulating the size of the aperture through which the water flows, it can be made to work slow or fast so as, within considerable limits, to measure accurately and legibly long or short intervals of time.

The disadvantages of the clepsydra were, first, that the hole in the container tended to become worn away so as to let the water out too fast; and second, that the water ran faster from a full vessel than from one nearly empty, because of the greater pressure. This latter was in classic times corrected by a clepsydra consisting of two vessels. The second and larger of these was placed below, the water running into it, out of the first. A float within this larger vessel rose regularly as it filled, and carried a pointer which marked the time. The first vessel from which the water ran into the second, was provided with an overflow, and kept constantly full up to this level; so that the flow of water into the larger vessel remained constant.

Once well established and understood in principle, the clepsydra became widely known over the ancient world, and underwent a variety of improvements and modifications in form. These latter chiefly dealt with making it more legible. Means were devised, for instance, to make it ring a bell when the water reached a certain height. And thus the alarm principle was very early brought into use. Later on, after the development of mechanical devices like the pulley and the toothed wheel or gear, the pointer was by these means constructed to move faster or slower than the rate at which the water rose, or to revolve upon a circular dial on which the hours were marked. And thus we owe to the clepsydra the origin of the modern clockface as well as of the alarm. Later still, by a more complex ingenuity, devices were arranged to strike the hours or to move mechanical figures, in fact, to perform all the functions of a clockwork which was both driven and regulated by hydraulic power. The single hour hand, however, remained in place of our two or three hands moving at different speeds, as in the modern clock or watch. The clockwork also remained primitive in construction compared with our own. Clepsydrae were always expensive, because accurate mechanical work was never cheapened until modern time. Rather they were made marvels of patient ingenuity and lavish ornament. Cunning oriental craftsmen spent their skill upon elaborate mechanism and costly decorations. The clepsydra thus became first what other time-pieces later became—a triumph of the jeweler's craft—a gift for kings. And the Greeks, who beautified everything that they touched, made it at once more accurate and more artistic.

The clepsydra may thus fairly claim to have been the first mechanical device for measuring time, as contrasted with the sun-dial which was really an astronomical instrument; and thus the direct ancestor of the mechanical clocks of later days. Some authorities, indeed, on the strength of certain very ancient allusions to its use in China and elsewhere, claim for it an antiquity prior to the sun-dial itself. There seems, however, to be no reason for supposing that the discovery of a mechanical law like the regular flow of water antedated so obvious a discovery as the motion of a shadow upon the ground. The explanation is probably that the invention of the clepsydra did precede the scientific perfecting of the sun-dial by the inclinations of the gnomon; which may have taken place about the time of the correction of the Babylonian calendar in 747 B. C. Not long after this date we meet with frequent references to the placing of a clepsydra in the public square of some old city, or to its use in astronomical calculations. To this, of course, its property of running by night was peculiarly adapted.

Although the chief defects of the clepsydra were minimized by the use of the two vessels and by making the aperture through which the water ran of gold or some other substance which would wear away very slowly, yet there remained certain minor imperfections. The water could not be kept entirely from evaporating; it had to be emptied out at intervals and the reservoir refilled; its accuracy was affected by the expansion of the parts under change of temperature, or it might even freeze. These faults were obviated in the sand-glass or hour-glass which for short intervals of time was also more convenient.

The clepsydra remained in use until clocks became superior to it in accuracy. See Clocks, Interesting Old; Charlemagne; Vailly.

Clerkenwell—A district on the north side of the city of London within the metropolitan borough of Finsbury. It is distinguished as one of the great centers of the watchmaking and jewelers' industries in England and long established there. The Northampton Polytechnic Institute, Northampton Square, has a department devoted to instruction in all branches of the trade.

Click—The click, pawl, or dog, is a necessary accessory of a ratchet wheel. It is a finger, one end of which fits into the teeth of the ratchet, while the other is pivoted on its tangent. The ratchet is thus prevented from turning backward.

Clock—Specifically, a time-piece not made to be carried about but to stand upon a shelf or table, hang upon a wall or as built into a tower. Formerly the term signified particularly a time-piece which struck the hours. The word has its origin in the word for bell in Latin, gloccio; Teutonic, glocke; French, cloche; and Saxon, clugga. At one time the term was used to denote timekeepers driven by weights as distinguished from those driven by springs.

Clock-Watch—A watch which strikes the hours in succession, as distinguished from repeaters. Popular in the eighteenth century.

Clock, Banjo--A wall clock, so called from its shape, designed by Simon Willard, of Massachusetts and very popular in its time.

Clock, Bird-Cage—An old form of English clock whose manufacture has been discontinued—it is the oldest form of English clock still doing service. Its main feature is the endless chain drive. These clocks run thirty hours.

Clock, Bracket—A form of clock very popular in England during the reign of Charles II, made to stand on a bracket or table and intended to be seen from all sides. These clocks had either a handle on top or one on each side. They were very beautifully finished.

Clock, Candle—Wax or tallow candle, usually twelve inches long and marked with circular lines one inch apart. The candle would burn one inch every twenty minutes or three inches an hour. Invention credited to King Alfred the Great.

Clock, Grandfather's or Long-Case—A tall clock with an anchor escapement popular thru-out the later 18th and early 19th centuries in England and America. Its excellent timekeeping qualities are due to the very long and heavy pendulum which allows a small arc of vibration. Not often made at present.

Clock, Hood—A style of clock originating and very popular in Holland during the late 17th century. Made of various woods, carved and ornamented and named from the hood or dome on top.

Clock, Lamp—A long glass tube upright on a metal stand similar in shape to the old Roman lamps. Figures were painted on the tube to indicate the hours—"12" in the middle section, with "11" above and "1" below the "12." The lamp was filled with oil up to the hour at which it was lighted—then as the oil burned away the time was indicated. This form of clock was used at night in Dutch and German rural homes until a comparatively recent date.

Clock, Lantern—Same as Bird-Cage Clock.

Clock, Largest in World—The Colgate clock in Jersey City is claimed to be twice as large as the next largest clock in the world. Its dial can be read for four miles and weighs six tons. Its minute hand is twenty feet long and the tip of it travels more than half a mile per day.

Clock Mysteries—Glass Dial—A perfectly transparent dial behind which no movement was visible. The hands were caused to revolve by watch works and semi-circular weights in the counterpoise of the hands.

Clock, Oldest in America—A clock owned by the Philadelphia Public Library—over two centuries old. It was made in London and is said to have been owned by Oliver Cromwell.

Clock, Sheep's-Head—A clock similar to the bird-cage or lantern clock in which the dial face projects an inch or two beyond the frame.

Clock, Skeleton—A clock whose works are covered with glass as a protection from dust, but are without a case, the works being exposed to view. There are eight skeleton clocks in the Charles Mifflin Hammond collection at the Essex Institute in Salem, Massachusetts.

Clock, Turret—A large clock in which the dials are distinct from the movement. Because of the exposure of the hands to the wind and snow, of the clock to dust and dirt, and of the oil to freezing temperature, turret clocks to keep time must be fitted with some device to obtain a constant force on the pendulum. The first used was the remontoire but since the invention of the gravity escapement for the Westminster clock by Sir Edmund Beckett this has been used instead.

Clock, "Wag on the Wall"—A wall clock typical of the North of Holland in which weights and pendulum hung below the clock case, entirely unenclosed.

Clock and Watch Makers, English, Early—For extensive lists, dates, places, and notes, see: Old Clocks and Watches & Their Makers, by Frederick J. Britten; Worshipful Company of Clockmakers, London, Published by E. J. Francis and Co., London, 1875; Old Clock Book, by Mrs. N. H. Moore.

French, Early—See: Old Clocks and Watches and Their Makers, by F. J. Britten.

Scottish, Early—For extensive list with dates, places and notes, see: Old Scottish Clock Makers, by John Smith.

Clock Makers, American, Early—For lists, dates, places, and notes, see: Old Clock Book, by Mrs. N. H. Moore; American Clockmaking—Its Early History, by Henry Terry.

Clock Mysteries; Tortoise in Water—Nicholas Grollier during the first part of the eighteenth century made many mysterious timekeepers. One was a metal dish filled with water in which floated the figure of a tortoise always keeping his nose to the correct time.

Ball of Venice—This was a sphere—its upper and lower parts gold, and about the middle a silver band bearing the numerals. As the band revolved a Cupid's wing pointed to the hour. Its action was simple. The cord which suspended it was wound about a cylinder. The weight of the ball constituted the driving power. It had a verge escapement. The maker is not known.

Double Globe—Constructed of two clear glass globes, the smaller one for the minutes above the larger hour globe. The mechanism for the latter was in the base, and for the minute globe, in the cap of the hour globe. Made by Henri Cunge.

Clocks, Interesting Old: Anne Boleyn's—A clock said to have been presented to Anne Boleyn by Henry VIII on their wedding morning. It is about four inches square and ten inches high, of silver gilt "richly chased, engraved, and ornamented." The weights are of lead covered with copper, gilt and engraved. On one are Henry's and Anne's initials, and true lovers' knots. On the other simply H. A. At the top of each weight is "Dieu et mon droit," at the bottom "The most happye." On the top of the clock is the figure of a lion holding the arms of England, the same being engraved on the sides. The clock is now silent. There is no record as to its maker.

Canterbury—This was the third of the large clocks in England. It was constructed in 1292.

Charlemagne's—In 807 the King of Persia sent Charlemagne a bronze water clock inlaid with gold. The dial consisted of twelve small doors representing the hours. Each door opened at the hour it represented and the correct number of balls fell out upon a brass bell. At twelve o'clock twelve horsemen appeared and shut the doors.

Coblentz—At Coblentz in a tower on the Kaufhaus is a brazen head which gnashes its teeth as the hours strike. For a Coblentzer to say "How is the man in the Kaufhaus" means "How goes it with Coblentz and the good people there?"

de Vick's—In 1364 Henry de Vick set up a clock in the tower of the palace for Charles V. It was regulated by a balance. The teeth of the crown wheel acted upon two small levers called pallets which projected from and formed part of an upright spindle or staff on which was fixed the balance. The clock was regulated by shifting the weights placed at each end of the balance. On the bell of this clock the signal for the massacre of St. Bartholomew's was struck.

Dondi's at Pavia—Built in 1344, by James Dondi, similar to Wallingford's clock.

Exeter—A clock built in Exeter Cathedral sometime in the 14th century. One erected there in 1480 has the sun—a fleur-de-lis which points out the hours as it revolves around a globe representing the earth. A black and white ball represents the moon's phases by turning on its axis.

Frederick II—The Saladin of Egypt presented Frederick II of Germany with a clock in the year 1232. It resembled internally, a celestial globe, in which figures of the sun, moon, and other planets moved impelled by weights and wheels. There were also the twelve signs of the Zodiac which moved with the firmament.

Hans von Jena's—An old clock in Saxony at the top of which is a very ugly head. As the clock strikes a pilgrim offers an apple on a stick to the open mouth and then withdraws it. At the same time an angel opposite the pilgrim raises her eyes from her book. The legend goes that Hans von Jena, for a crime, was condemned to undergo such torture for three centuries.

Jefferson's—An old weight clock in which the weights are carried over a pulley and made to indicate the day of the week by their position. This is in the hallway at Monticello.

Lists and Descriptions of—See Curiosities of Clocks and Watches, E. J. Wood. Old Clocks and Watches and their Makers, F. J. Britten. Old Clock Book, N. H. Moore.

Vase Clocks of Marie Antoinette—The movement was inclosed in a marble pedestal. About the beautifully tinted porcelain urn was a double band, on which were marked the numerals and which revolved every twelve hours. A serpent with head erect pointed to the hour.

Mary, Queen of Scots—Skull Watch or Clock. A small clock in the form of a skull said to have been given by Mary, Queen of Scots, to Mary Seaton, one of her maids of honor. The skull is of silver gilt and is engraved with figures of Death, Time, Adam and Eve, and the Crucifixion. The lower part of the skull is pierced to emit the sound when it strikes, being cut in the form of emblems of the Crucifixion. The works occupy the brain's position in the skull fitting into a silver bell which fills the entire hollow of the skull. The hours are struck on this bell by a small hammer on a separate train.

Pope Sixtus'—Built by Habrecht of Strasburg in 1589. It greatly resembles the Strasburg clock which Habrecht also built. It was in the possession of the Popes for more than two centuries and later became the property of William I, King of the Netherlands. In 1850 it was exhibited in England after which it became the property of Mr. O. Morgan. It performs all the feats of the Strasburg clock.

Rouen—In the Rue de la Grosse Horloge in Rouen a clock made by Jehan de Fealius in 1389 is built in a tower which surmounts an arched gateway. Its dial is about six feet square. It shows the hours, days of the week, and phases of the moon. It still keeps excellent time and is the chief clock of the city.

St. Dunstan's—Erected in 1671 above the gateway of the old St. Dunstan's Church. The clock had two dials, back to back upheld by a quaint bracket. In a little open belfry above were the gaily painted figures of Gog and Magog which struck the quarters on bells suspended near them. In 1830 the clock was sold to the Marquis of Hertford who set it up at his home in Regent Park.

St. Paul's—A clock existed prior to 1298 in the tower of St. Paul's Cathedral which struck the hours by means of mechanical figures called Paul's Jacks. Later a fine dial was added.

Strasburg—Rebuilt twice after the first one which was begun about 1352. This first clock consisted of a calendar which showed the principal movable feasts. It showed also the movements of the sun and moon. On the upper part was a statue of the Virgin before which at noon the figures of the three Magi bowed. At the same time a cock automaton opened its beak, flapped its wings and crowed. 2. The second Strasburg clock was erected about 1570. This was a very elaborate mechanism, showing besides the time, a calendar for a century, the movements of the sun and moon, eclipses of the same and other things. The striking was done by an elaborate automatic arrangement. (See Old Clocks and Watches & Their Makers—F. J. Britten.) 3. In 1842 the clock was again thoroughly reconstructed. This, too, is a very elaborate system of motions showing the movements of sun, moon, and planets, also sidereal time, a calendar, etc. The hours and quarters are struck by automatic figures.

Ulm—In the eastern end of the old Rathaus at Ulm is installed an astronomical clock which dates from the beginning of the 16th century. It was thoroughly repaired in 1549 by the builder of the Strasburg clock—Isak Habrecht. Shows in addition to the hours, the diurnal and annual revolutions of the earth and the movements and phases of the moon. The clock is an artistic achievement as well as a mechanical wonder.

Vailly's—A scientific water clock. It consisted of a tin cylinder divided into several small cells and suspended by a thread fixed to its axis, in a frame on which the hour distances fixed by trial were marked. It was so made that the water passed slowly from one cell to the next and as it did so it changed the center of gravity of the cylinder and set it in motion so as to indicate the time on the frame. Made about 1690.

Wallingford's—Built in 1326 in St. Alban's Monastery. It showed besides the hours, the apparent motion of the sun, the ebb and flow of tides, changes of moon, etc. It continued to run until the time of Henry VIII. Held by some to have been a mere planetarium.

Wells Cathedral—Clock built by Peter Lightfoot, A. D. 1340 at Glastonbury and removed to Wells Cathedral during the Reformation, after the dissolution of the Glastonbury monastery. In 1835 it was again removed to the South Kensington museum. At that time the worn-out works were replaced by a new train, but the dial and knights were retained. The dial is divided into twenty-four hours and shows the motion of the sun and moon. On its summit are eight armed knights tilting at one another, lance at rest by a double rotary motion.

Westminster—A clock said to have been erected at Westminster with the proceeds of a fine imposed upon one of the Chief Justices about 1288. About 1365 Edward III had a stone clock tower erected at Westminster. This tower contained a clock which struck the hours on a great bell. It also contained other bells. This tower was razed by the Roundhead mob about 1650. Later a dial with the motto "Discite justiam monite" was placed on the site. The bell "Great Tom" was given to St. Paul's about the beginning of the 18th Century. The present Westminster clock is made after plans by E. B. Denison (Sir Edmund Beckett) and made by E. J. Dent. The bell is called "Big Ben." It is claimed to be the best timekeeper of its kind in the world. It was for use in this clock that Denison invented his gravity escapement.

Wimborne—A very old clock at Wimborne in Dorsetshire, much like the Wells Cathedral clock. By some authorities believed also to have been planned by Peter Lightfoot.

Clock-Setters—During the early history of turret clocks, for each one was employed a caretaker called the "setter." That such an official was needed indicates that they were more or less undependable.

Cock—A horizontal bracket. See: Balance Cock; Escape Cock; Pendulum Cock; Potance.

Collet—A collar or flange on a cylindrical piece of metal. Any part of such cylinder of greater diameter than the rest. Sometimes of the same piece of metal; sometimes fitted friction tight upon it.

Compensation—The provision made in a clock or watch to counteract the expansion and contraction due to variations of temperature. In the clock it is applied to the pendulum; in the watch to the balance.

Compensation Balance—A balance corrected for errors caused by variations in temperature. The type in most general use was invented by Thomas Earnshaw in the second half of the 18th century. The double rim of this balance is constructed of brass and steel soldered together in the form of a cut ring, the brass on the outside. When heat, elongating the balance ring, causes it to vibrate more slowly, the brass, expanding more than the steel, bends the free ends of the cut rim toward the center, thus decreasing the diameter of the balance and quickening the vibration. On the other hand, when cold, contracting the ring tends to quicken the vibration of the balance, the contraction of the brass rim draws the free end outward, making the diameter larger and the vibration slower in consequence. The compensation balance is also made with brass as the inner metal and aluminum outside.

Compensation Curb—A laminated bar of brass and steel or aluminum and brass fixed at one end, the free end carrying the curb pins that regulate the length of the balance spring. Common in old watches but not now in use.

Compensation Pendulum—A pendulum so constructed that the distance between the point of suspension and the center of oscillation remains constant in all temperatures. See: Pendulum, Gridiron and Pendulum, Mercurial Compensation.

Contrate Wheel—A wheel whose cogs are parallel to its axis and whose axis is at right angles to the axis of the wheel into which it gears. A crown wheel.

Corrosion—The eating or wearing away of metals by slow degrees through chemical action.

Countersink—To enlarge the outer end of a hole for the reception of the head of a screw, bolt, etc. The term is also applied to the tool with which the countersink is formed.

Coventry—A municipal, county, and parliamentary borough of Warwickshire, England. One of the important watchmaking centers of Great Britain.

Crown Wheel—A wheel whose teeth project at right angles to the plane of the wheel. A contrate wheel. The escape wheel of the verge escapement is an illustration.

Crutch—A light rod in a clock descending from the pallet arbor and ending in a fork which embraces the pendulum rod. It transmits the motion of the pallet to the pendulum.

Ctesibus—A famous Greek mechanician who lived in Alexandria about 130 B. C. Although his was not the first clepsydra as is claimed by some it was an ingenious and interesting one. Believed to have first applied toothed wheels to clepsydrae about 140 B. C.

Curb Pins—See Banking Pins.

Cusin, Charles—A watchmaker from Autun, Burgundy, who laid the foundation for the Swiss watch industry in Geneva in 1587. It grew very slowly at first—in 1687 having only one hundred watchmakers with three hundred assistants. In 1760 there were at Geneva eight hundred watchmakers with 5,000 to 6,000 assistants.

Custer, Jacob D.—(1809-1879.) A Pennsylvania clockmaker in 1831; he was one of the early makers of watches in America in 1840. However, his work was not important commercially, for he produced only about a dozen watches. A very ingenious man, who, it is said, made everything from a steam engine to his own shoes. He made hundreds of the clock movements which at that period were used to revolve the lanterns in lighthouses.

Cycle of the Sun—A period of twenty-eight years, after which the days of the week again fall on the same days of the month as during the first year of the former cycle. It has no relation to the sun's course but was invented for the purpose of finding out the days of the month on which the Sundays fall during each year of the cycle. Cycles of the sun date from nine years before the Christian era.

Cycloid—A curve generated by a given point in the circumference of a circle which is rolled along a straight line always in the same place. Example: The curve traced by any point in the rim of a wheel which travels in a straight line along a level road.

Cylinder Escapement—See: Escapement, Cylinder.

Cylinder Plugs—Plugs fitted into the ends of the cylinder of a cylinder escapement. Their outer extremities are formed into the pivots on which the cylinder rotates.

Damaskeen—To decorate a metal by inlaying other metals or jewels, or by etching designs upon its surface. To be distinguished from snailing, with which it is often confounded.

Day—The time of one complete revolution of the earth on its axis. The actual length of this day is continually changing owing to the eccentricity of the earth's orbit and the angle of the ecliptic. The mean solar day is 24 hours. The sidereal day is 23 hours, 56 minutes, 4.099 seconds.

Day, Nautical—The nautical day begins when the sun is on the meridian and eight bells are struck. The day is divided into "afternoon watch" or four hours, two "dog watches" of two hours each, then "middle watch," "night watch," "morning watch" and "forenoon watch," each of four hours, completing the day.

Denison, Edmund Beckett—Sir Edmund Beckett—Lord Grimthorpe. Born 1816. A lawyer by profession, and the inventor of the gravity escapement for turret clocks; also an authoritative writer on horological subjects. He designed and planned the Westminster clock said to be the best timekeeper of its kind in the world. Died 1905.

Dennison, Aaron L.—Born in Freeport, Me., in 1812. Died Birmingham, England, January 9, 1898. At eighteen he was apprenticed to a watchmaker. Later in working at the trade, he was impressed with the inaccuracies which existed in the best handmade watches. This, with a visit to the Springfield Armory, gave him his idea of machine-made watches with interchangeable parts. He interested Edward Howard in the project, and having found the needed capital they started in the business and laid the foundation of what is now the Waltham Watch Company. Dennison has been called the "father of American Watchmaking" tho there seems ground for the claim that he shares that honor with Edward Howard.

Depthing—The technical name for the proper adjusting or spacing of the gearing in a watch.

Detent—The device which halts, and releases, at the proper instant the escapement of a clock or chronometer. See: Escapement.

de Vick, de Wyck, or de Wieck, Henry—A German clockmaker who, in 1364, made the first turret clock of which reliable information and description remains. The clock was made for Charles V. See: Clocks, Interesting Old—De Vick's.

Dial—Commonly called the face of the watch—made of gold or silver or other metal or of enamel, with the required figures—in the United States one to twelve upon it in a contrasting color. See also, Sun-dial.

Dial Feet—Short wires soldered to the back of the dial of a watch or clock which hold it in place by fitting into holes in the pillar plate.

Dial of Ahaz—A sun-dial belonging to Ahaz, King of Judea 742-727 B. C., mention of which occurs twice in the Scriptures—II Kings, XX: 9-11, and Isaiah XXXVIII: 8. It is believed that one of his Babylonian astrologers constructed it for him.

Dial Plate—See Lower Plate.

Dial, Sun—See Sun-dial.

Dial Wheels—The wheels constituting the motion work of a watch.

Diurnal—In an astronomical sense, pertaining to a period covering a mean solar day. See: Solar Time.

Dog Screw—A screw with an eccentric head used to attach a watch movement to a dome case.

Dog-Watch—A nautical term for two daily two-hour periods of watching aboard ship. The first begins at 4 P. M., the other at 6 P. M.

Dolmen—A sacred instrument used for astronomical purposes at certain critical periods of the year; formed of four stones at the cardinal points and a leaning stone crossing diagonally and forming with the east stone a sacred "creep-way." The solar hours were indicated by the shadow of the leaning stone touching various prominent points or edges. One at Camp, England, is prehistoric.

Dome—The inner case of a watch which snaps on the band of a case.

Dome-Case—A case in which the inner case or dome snaps to the band of the case.

Dondi, Giacomo—Born at Padua, Italy, in 1298. In 1344 he set up at Padua a famous clock which became a model for later clocks and which earned for him the surname, "Orologio."

Double Bottom Case—A watch case in which the inner cover or bottom is made solid with the middle. The vogue in English cases for a long time; now almost obsolete.

Double-Sunk Dial—A dial in which there are two sinks; one for the hour hand, and a deeper one for the seconds hand.

Draw—1. The force which holds the lever against its bank, due chiefly to the angle of the locking face of the pallet stone. 2. The angle of the locking faces of pallets in the lever escapement.

Driver—Of two wheels working together, the one which imparts the power. The driven wheel is termed the follower.

Driving Wheel—In a clock the wheel on the main arbor which drives the whole train.

Drop—That part of the motion of the escape wheel when it is not in contact with the pallet.

Drum—The cylinder, or barrel, on the main arbor in a clock on which the driving cord winds, raising the weight, when the clock is being wound.

Dummy Watch—(Fausse Montre.) About 1770 it became the fashion to wear two watches. But because two real watches were too expensive for most people, the custom grew up for having one sham watch—usually worn on the right side. These were called "dummy watches" or "fausse montres."

Earnshaw, Thomas—1749-1829. An eminent English watchmaker who invented the spring detent escapement and the compensation balance, both essentially the same as are now used in chronometers. He first soldered brass and steel together for the balance instead of riveting them.

East, Edward—Watchmaker to Charles I and an eminent horologist. He was one of the ten original assistants named in the charter of the Clockmakers' Company and at once took a leading part in their proceedings. He was elected master in 1664 and 1682. He was the only treasurer ever appointed by that company. He died probably about 1693. East's watches were often presented as prizes by Charles in tennis tournaments.

Edward VI—King of England from 1546 to 1553. Said to have been the first Englishman to wear a watch.

Electric Clock—A clock in which the pallets moved electrically from a distant mechanism drive the escape wheel and the hands.

Ecliptic—That plane passing through the center of the sun in which lies the orbit of the earth. Also used to designate the apparent path of the sun in the heavens.

Elgin—A city in Illinois, U. S. A., in which is located the Elgin National Watch Company—one of the largest factories in the United States.

End-Shake—Freedom of pivots to move endways. Necessary in a watch or clock because there is no force to spare and a tight pivot would stop the movement.

End-Stone—A small disc of jewel against which the end of a pivot sets. See Capped Jewel.

End-Stop—In a watch the same as end-stone.

Engaging Friction—Friction which results when the teeth of two wheels gearing together come into action before reaching the line of centers—that is, a line drawn from center to center of the gearing wheels.

Engine-Turning—A pattern of curved lines cut into metal for decoration. Introduced about 1770 by Francis Guerint of Geneva. The earliest specimens were cut very deep but shallower cutting soon became the rule.

Engraving—A form of ornamenting metals in which the design is cut into the metal. In "Champ-leve" engraving the ground is cut away leaving the design in relief.

Epact—The excess in time of the solar year over the period of 12 lunar months, amounting to about 11 days. The new moons will thus fall about 11 days earlier in each succeeding year. In a calendar so arranged 30 days are taken off every fourth year, as an intercalary month, the moon having revolved once in that time, and the three days remaining would be the epact. The epact thus continues to vary until at the end of nineteen years the new moons return as at first.

Epicycloid—A curve generated by any point in the circumference of a circle as it rolls on the outside of the circumference of a fixed circle. This curve is the best for the face of the teeth of a driving wheel.

Equation Clocks—An obsolete form of clock which showed true solar or sun-dial time instead of mean solar, or average time.

Equation of Time—The difference between true time and mean, or averaged time. There are four days in the Gregorian year when the true time and mean time agree, and the equation of time is zero: These are December 24, April 15, June 15, and August 31. Between the first two dates and the last two dates, true time is earlier than mean time; for the other two periods of the year it is later.

Escape Cock—The bracket which supports the upper ends of the escape wheel and pallet staff arbors.

Escapement—The device in a watch or clock which regulates the motion of the train thus distributing the power of the main-spring. It communicates the motive power to the balance or pendulum. Escapements are of three classes: recoil, dead, or dead-beat; and detached.

Escapement, Anchor—The recoil escapement, invented by Hooke, used in most house clocks. A name also applied to one kind of Lever Escapement with an unusually wide impulse pin. The recoil escapement is one in which each tooth of the escape wheel, after it comes to rest, is moved backward by the pallets. Altho one of the easiest escapements to set out correctly the pallets are often improperly formed making an escapement which gives indifferent service. As a timekeeper the anchor escapement is inferior to the dead-beat escapement.

Escapement, Chronometer—A detached escapement in which the escape wheel is locked on a stone carried in a detent, and in which the teeth of the escape wheel impart an impulse to a pallet on the balance staff with every alternate vibration. Used in Marine Chronometers.

Escapement, Crown-Wheel—Of the recoil type, and the earliest known escapement; to be found in Henry de Wyck's clock. Not suitable for watches. Practically the same principle as Verge or Vertical Escapement used in watches for so many years.

Escapement, Cylinder or Horizontal—Invented by Thomas Tompion in 1695—later improved and brought into general use by Graham. It dispensed with the then common vertical crown-wheel—hence the term "horizontal" and permitted thinner watches. This escapement is frictional, the balance being carried on a hollow cylinder whose bore is large enough to admit the teeth of the escape wheel. The cylinder is cut away where the teeth enter and the impulse is given by the wedge shaped teeth striking against the edge of the cylinder as they enter and leave. Used at this time in the cheaper Swiss watches.

Escapement, Dead-Beat—Any escapement in which the pallet face is so formed that the escape wheel remains dead or motionless during the supplementary arc of the balance or swing of the pendulum. As invented by George Graham, the wheel is much the same as the wheel in the anchor escapement, the difference lying in the shape of the pallets. Each pallet has a driving face and a sliding face. It is so arranged that the impulse is given the pendulum at the midpoint of its swing thus allowing the swing to adapt itself to the impulse and keep the time constant. The pallets are faced with jewels so that there is slight friction. Used in high grade clocks such as regulators and astronomical clocks.

Escapement, Detached—Any escapement in which the balance or pendulum is for some time during each vibration free from the pressure of the train. Detached escapements are used in chronometers, most watches and in turret clocks. They are of value in any movement where the motive power varies greatly—hence in turret clocks. Examples: Chronometer, lever, and gravity escapements.

Escapement, Double Three-Legged Gravity—Invented in 1854 by E. B. Denison, Esq., for the great clock at the Houses of Parliament. It is the best escapement for very large clocks where the hands are exposed to the action of the wind and snow, because it admits of great driving power in the movement without its sensibly affecting the escapement as would be the case in the dead-beat type. The impulse to the pendulum is given by the weight of the lever arms falling through a given distance and is therefore constant. This escapement consists of two gravity impulse pallets pivoted in a line with the bending point of the pendulum. There is a locking wheel made of two thin plates of three teeth each. Between these plates are the three pins that lift the pallets. The locking is effected by blocks screwed to the front of one pallet and the back of the other. Impulse is given by the pallets in turn striking the pendulum rod. The pendulum rod serves to unlock the wheel. The arrangement is such that the lifting pins have a little free run each time. Since the pallets are always lifted the same distance they give a constant impulse to the pendulum.

Escapement, Duplex—Invented by Hook; later improved by Tyrer. Very accurate but as originally made was affected by any sudden motion, and hence of little use in watches. The escape wheel has two sets of teeth. Those farthest from the center lock the wheel by pressing on a hollow ruby cylinder fitted round the balance staff and notched so as to permit the passing of the teeth as the balance moves in a direction opposite to the wheel's motion. The second set stand up from the face of the wheel and one gives impulse to the pallet every time a tooth leaves the notch. This is not a detached escapement, but there is little friction. As improved this escapement was used in the famous Waterbury watches.

Escapement, Foliot—A form of escapement actuated by a foliot balance. See Foliot.

Escapement, Four-Legged Gravity—Invented by E. B. Denison (Sir Edmund Beckett). The same in principle as the Double Three-Legged escapement, only it has but one escape wheel with four teeth or legs instead of two wheels with three legs each. The wheel has two sets of lifting pins—one acting on each pallet. Occasionally used in regulators and other clocks with a seconds pendulum, but of doubtful, if any, advantage over the Graham dead-beat escapement.

Escapement, Frictional—Any escapement in which the balance is never free from the escapement. Examples: The Cylinder, Duplex and Verge types.

Escapement, Gravity—An escapement which gives impulse to the pendulum by means of a weight falling through a constant distance. Of use in turret and other exposed clocks where the hands' movements are affected by wind, rain, and snow. See subtitles under these headings: Double Three-legged Gravity; Single Three-legged Gravity; Four-legged Gravity; Six-legged Gravity.

Escapement Lever—Invented by Thomas Mudge about 1765. It is the preferred escapement for watches because of the certainty of its performance. Possibly inferior to the chronometer escapement as a timekeeper. Its most noticeable defect is the necessity of applying oil to the pallets, the thickening of which affects the action. There are many other kinds of lever escapements. The Mudge escapement was essentially like the modern Double Roller. The connection between the balance and the escape wheel is made by a lever to which the pallets are fastened, and into the forked end of which plays the ruby pin which is carried on a roller on the same staff as the balance. Each pallet has an impulse face and a locking face. The impulse is given by the escape wheel tooth striking the impulse face of a pallet and is communicated to the balance by the lever, raised by the pallet's movement striking the ruby pin in the roller. This ruby pin also serves to unlock the pallets by causing the lever to lift them in turn. This escapement is of the detached type. The action of the lever is kept within the desired limits by banking pins.

Escapement, Lever—Club Tooth—An escapement like the Table Roller in the action of the lever and roller, but differs in the pallet action. The impulse planes are partly on the teeth and partly on the pallet. This is the standard watch escapement of today.

Escapement, Crank Lever—An escapement with a small roller having a tooth like a pinion leaf projecting from its circumference. This tooth acts in a square notch cut in the end of the lever. The lever is formed like a fork the two points of which act as safety pins against the edge of the roller to prevent the lever from getting out of action with the roller. It necessitated very careful construction and was not so good as the Double Roller or Table Roller.

Escapement, Lever—Double Roller—This escapement has two rollers on the balance staff, the large one carrying the balance staff and the small one used for a safety roller only. The best form of lever escapement but more delicate, expensive, and difficult to make than the Table Roller; hence not so much used as the latter.

Escapement, Patent Detached Lever—Introduced in 1766 by Thomas Mudge, but neglected for years thereafter even by Mudge himself. It was in some of its parts the model of the best form of lever escapement—the Double Roller. The first pallets had no "draw" on the locking faces which rendered the escapement peculiarly sensitive to jolt and jar. This may have suggested to Mudge the addition of the small roller, whose worth has been since unquestionably demonstrated.

Escapement, Lever—Pin-Pallet—A lever escapement with round pins for pallets, and the inclines on the escape teeth. Used in alarm clocks.

Escapement, Rack-Lever—Invented by Abbe Hautefeuille in 1734. Afterward made and improved by Berthoud and by Peter Litherland, who obtained a patent for it in 1794. It consisted of anchor shaped pallets on whose axis was fixed a rack, or segment of a toothed wheel which geared into a pinion on the axis of the balance. The balance was thus never free from the train and good timekeeping was made impossible. It is not now in use.

Escapement, Lever-Resilient—Invented by F. J. Cole about 1870. A form of lever escapement designed to obviate the evils of overbanking. The points of the escape-wheel teeth are bent toward the locking faces of the pallets, the bend in the tooth acts as the banking and no pins are required. It was abandoned because expensive to make and the danger of overbanking is not considerable.

Escapement, Lever—Table Roller—Excellent and very simple and the most common form today. It differs from the crank lever only in the action of the roller. The impulse pin instead of projecting beyond the edge of the roller is set within its circumference and raised above its plane.

Escapement, Lever—Two Pin—A form of Lever Escapement in which the unlocking and impulse actions were formerly divided between two small gold pins in the roller and one in the lever. Later the two roller pins were discarded, and one broad jewel pin substituted.

Escapement—Pin Wheel—Invented by Lepaute about 1750. Similar in action to the dead-beat. A good and simple escapement for large clocks. The impulse is given the pendulum through the pallets by pins which stand out from the face of the escape wheel. Lepaute made these pins semi-circular and had his pallets of equal length acting on opposite sides of the wheel. Sir E. Beckett cut away part of the front of the pins which allows the pallets to act as in the diagram. The resting faces are arcs of a circle. It has been superseded by the gravity escapement for large clocks and is inferior to the dead-beat for small.

Escapement, Recoil—Any escapement in which the pallets actually force the escape wheel to turn backwards a trifle with each beat of the balance. Cheap and easy to make but inferior as timekeepers to the detached or dead-beat types.

Escapement, Right-Angled—A lever escapement so set that lines drawn between the centers of the balance, pallets, and escape wheel would form a right angle. See Escapement, straight-line.

Escapement, Single-Beat—An escapement such as the Duplex, or Chronometer, whose escape wheel moves only at alternate beats of the balance or pendulum.

Escapement, Single Three-Legged Gravity—Consists of two pallets and one three-legged locking wheel. Instead of the three pins for lifting as in the Double Three-Legged Gravity escapement there is a triangular steel block which acts against large friction rollers, pivoted one on each pallet.

Escapement, Six-Legged Gravity—A modification of the three-legged gravity escapement. The locking wheel has six teeth. One of the pallet arms is neutral and gives no impulse, hence impulse is given only at each alternate vibration. A much lighter driving weight than for the Double Three-legged Gravity escapement will suffice for this, since the rotations of the escape wheel required are only half as many.

Escapement, Straight-Line—An escapement of the lever type in which the escape wheel, pallets and balance are all in a straight line; an arrangement favored by the Swiss.

Escapement, Verge—Also called "Crown-wheel," or Vertical escapement. The earliest form of escapement on record. The inventor is not known, but the escapement was used on de Vick's clock. (1364.) It was used almost exclusively up to 1750 in spite of its manifest inaccuracy. The verge is a frictional recoil escapement. It consists of a crown-wheel, with eleven, thirteen, or fifteen teeth, shaped like those of a rip saw, and with its axis set at right angles to the pallets axis, or verge, which carries the balance. The verge is a slender cylinder as small as compatible with the required strength, from which project the pallets, two flat steel "flags"—at an angle to each other varying from 90° to 115°. The wheel runs in a watch in a plane at right angles to the face. Any variation in the motive power causes a variation in the arc of the balance swing. Therefore, since the time of oscillation depends on the arc of the swing, the time-keeping qualities were directly affected. This gave rise to the invention of the stack-freed and fusee, both contrivances to equalize the power of the mainspring. In spite of the many defects the verge escapement was one of the great inventions because the first escapement, and was used for centuries before superior kinds were devised. It necessitated thick and bulky watches.

Escapement, Virgule—An early form of escapement invented about 1660 by Abbe Hautefeuille. Its action can be readily understood from the diagram.

Escape Pinion—The pinion on the escape-wheel arbor.

Escape Wheel—The last wheel of a train: it gives impulse to the balance, indirectly. Also called scape wheel. Easily identified by teeth resembling those of a circular saw.

Face—1. Of a watch or clock is the dial. 2. Of the tooth of a wheel, that portion beyond the pitch line.

Facio, Nicolas—A Geneva watchmaker who invented the art of piercing jewels for use in watches, and in May, 1705, obtained a patent therefor in London. In December of the same year when he petitioned for a more extended patent he was opposed by the Clockmakers' Company, who produced in evidence proof that Facio was not first in this use of jewels, in an old watch of Ignatius Huggeford's with an amethyst mounted on the cock of the balance wheel. Facio's petition was denied. It was later discovered that Huggeford's jewel had nothing to do with the mechanism of the watch.

Favre, Perret E.—In 1876 the chief commissioner in the Swiss Department and a member at that time of the International Jury on Watches at the Centennial Exhibition at Philadelphia. On his return home he was very emphatic in his endorsement of the American method of manufacture as compared to the Swiss.

Fitch E. C.—Made president of the Waltham Watch Co., in 1886. His long experience in watch case and movement making and his commercial training made his judgment on matters relating to watchmaking of value. He was the inventor of the screw bezel case.

Flank—The flank of a wheel or pinion is the part lying between the pitch circle and the center.

Flirt—Any device for causing the sudden movement of a mechanism.

Fly—A speed regulating device or governor consisting of a fan or two vanes upon a rotating shaft. Used in the striking part of clocks. By some believed to have been used on the earliest clocks—before the verge escapement—to check a too rapid descent of the weight.

Fly Pinion—The pinion in a clock that carries the fly: a part of the striking mechanism.

Fob—Properly a watch pocket in the waistband of trousers. Commonly applied to the end of a chain or ribbon which is attached to the watch and hangs free from the pocket. One of the early examples was attached to a watch made for Oliver Cromwell in 1625 by John Midwall in Fleet Street.

Foliot—A straight armed balance with weights used as one of the earliest clock regulators. De Vick's clock is one example of it.

Foliot Balance—See Foliot.

Follower—Of two wheels geared together, the one to which the driver imparts motion is called the follower.

Fork—The fork shaped end of the lever into which plays the roller jewel.

Fourth Wheel—The wheel in a watch that drives the escape pinion and to whose arbor the seconds hand is attached.

Frame—The plates or plate and bars of a watch or clock which support the pivots of the train.

Free Spring—A balance spring not controlled by curb pins. Used in chronometers and other fine time pieces where the spring is an overcoil.

Fromanteel, Ahasuerus—A clockmaker of Dutch extraction—maker of steeple clocks in East Smithfield. The family of Fromanteels were celebrated as having been the first to introduce the pendulum clocks into England. Their claim has since been contested in favor of Harris and Hooke.

Full Plate—A model in which the top plate is circular in form—the balance being above this plate. Used now in 18 size watches for railroad and other hard usage. They are made only in limited quantities.

Fusee—Invented by Jacob Zech of Prague about 1525. Consists of a specially grooved cone-shaped pulley interposed between the mainspring barrel and the great or driving wheel of a watch or clock. The connection between the barrel and fusee was first made by a cord or catgut, later by a chain. In winding the spring the cord is drawn from the barrel on to the fusee—the first coil on the larger end. Thus the mainspring when fully wound uncoils the cord first from the smaller end of the fusee; and as it runs down gets the benefit of increased leverage by reason of the greater diameter of the lower part of the fusee. An excellent adjustment of the pressure on the center pinion can be made in this way. The fusee has been abandoned in watches to allow of thinness, but is still used in chronometers and clocks.

Fusee Cap—A thin steel plate with a projecting nose on the smaller end of the fusee: a part of the mechanism to stop the fusee when the last coil of the chain is wound thereon.

Fusee Chain—A very delicate steel chain connecting the barrel with the fusee of a watch, chronometer or clock. It replaced the catgut originally used and was first introduced by Gruet of Geneva about 1664.

Fusee Sink—The sink cut in the top plate of a watch to give space for the fusee.

Galileo, Galilei—Commonly called "Galileo." A famous Italian scientist born in 1564 who discovered, among many other things, the isochronism of the pendulum vibrating through long or short arcs. The story goes that he noticed that a swinging chandelier in a certain cathedral took the same length of time to each vibration whether in long or short arcs—timing them by his pulse. He seems never to have applied this principle to clocks, although he issued an essay on the subject in 1639.

Galileo, Vincentis—Son of the great astronomer, born about 1600. He aided his father in experiments and gave special attention to the application of the pendulum to clocks. He is claimed by some to have been the first to so apply the pendulum, in 1649, but this is disputed in favor of Richard Harris of London.

Geneva—A city in Switzerland in which watchmaking was first established in that country. It is the center of the "hand" industry, and the city is honeycombed with garret-workers—so-called—making parts.

Gerbert (Pope Sylvester II)—Born in Belliac, Auvergne, in 920. In 990 Gerbert made some sort of a clock which attained wide fame. Some authorities claim that it was a clock moved by weights and wheels and some even claim for it a verge escapement. On the other hand, other authorities state positively that that story is a myth and that Gerbert's horologe was a sun-dial. It seems pretty well accepted that there was no escapement used, however, until more than two centuries after Gerbert's time.

German Silver—An alloy of copper, nickel, and zinc—copper predominating. Really a white brass.

Gimbal—A contrivance resembling a universal joint permitting a suspended object to tip freely in all directions. Marine chronometers are supported in their cases or boxes by gimbals. It was first applied to chronometers by Huyghens.

Gnomon—A simple and probably the most ancient instrument for marking time consisting simply of a staff or pillow fixed perpendicularly in a sunny place—time being reckoned by the changing length of the shadow or by its angular movement. In more recent times the title "gnomon" was applied to the style of the sun-dial.

Gnomonics—The art of constructing and setting sun-dials taught especially in the seventeenth century.

Goddard, Luther—Born at Shrewsbury, Mass., February 28, 1762—Died 1842. He was the first American to manufacture watches. He began in 1809 but unable to compete as to price with cheap foreign watches, retired after making about five hundred.

Going-Barrel—The Swiss early abandoned the fusee in watches and cut teeth around the outside of the main-spring barrel so as to drive the train direct. Such an arrangement is called a going-barrel. It made possible a thinner and much simpler watch. American makers quickly adopted this device, but the English long clung to the fusee. It is sometimes claimed that the French were the first to adopt the going-barrel.

Going Fusee—A fusee with maintaining power attachment, so that the watch does not stop while being wound. Invented by Harrison.

Golden Number—Meton, an Athenian astronomer, discovered about 432 B. C. that every nineteen years the new and full moons returned on the same days of the month. This period is the cycle of the moon, called the Golden Number because the Greeks, to honor it, had it written in letters of gold. Anno Domini, the year of our Lord, fell on the second year of a lunar cycle. Hence, to find the Golden Number for any year, add 1 to the date (A. D.) and divide by 19. The remainder is the Golden Number for the year.

Gold-Filled—A sheet of brass sandwiched between two thin plates of gold and all brazed together. Gold-filled watch cases were introduced in America. They give very good wear.

Graham, George, F. R. S.—An English watchmaker and astronomer, born in Cumberland in 1675. Died 1751. He was an apprentice of Tompion and succeeded to Tompion's reputation as the best watchmaker of his time. He invented the mercurial compensation pendulum, the dead-beat escapement, and perfected the cylinder escapement of Tompion and left it in practically its present form. He made ornamentation distinctly subsidiary to use. He was master of the Clockmakers' Company in 1722-23. He was buried with Tompion in Westminster Abbey.

Great Tom—The great bell which struck the hours on the first clock at Westminster. It was afterwards transferred to St. Paul's.

Great Wheel—In a fusee watch the toothed wheel which transmits the power from the fusee to the center pinion. In a going-barrel watch it is represented by the toothed portion of the barrel drum.

Greenwich Observatory—(England) Royal observatory founded 1675 to promote astronomy and navigation. There is at this observatory a standard motor clock which is the center of a system of electrically controlled clocks scattered over the Kingdom, and which thus keeps official time as our Naval Observatory clock does for the United States.

Grimthorpe—See Denison, E. B.

Gruen, Dietrich—A Swiss watchmaker who with his son Fred first succeeded in making a very thin watch. The Gruen watch factory at Cincinnati, Ohio, is unique in this country. The buildings and surroundings resemble those of Switzerland, and the method of manufacture embodies more handwork than is common in the American system.

Gruet—A Swiss who introduced chains for the fusee instead of catgut cord, in 1664. They are still used for marine chronometers, some clocks, and the few fusee watches now made.

Guard Pin—A pin in a lever escapement which prevents the pallets leaving the escape wheel when the hands of a watch are turned back. Also known as the "safety pin."

Guild or Gild—An association of people occupied in kindred pursuits for mutual protection and aid. Watch and clockmakers belonged to the Blacksmiths' Guild in England until 1631, when the Clockmakers' Company was formed. In France the Clockmakers' Guild was powerful in 1544.

Hair-Spring—Said by some to be a distinctly American term for the balance spring of a watch. But Wood (English) uses it in his "Curiosities of Clocks and Watches," 1866. However, it is not in common use outside of America. It is thought to have originated from the fact that in early times attempts were made to utilize hog-bristle for the balance spring.

Half Plate—A watch in which the top plate covers but half of the pillar plate, the fourth wheel pinion being carried in a cock to allow the use of a larger balance. Now obsolete or nearly so. Replaced by the bridge-model.

Hall Mark—A stamp placed upon gold and silver articles by government officials after the metal therein has been assayed.

Hands—The metal pointers which, moved by the train, indicate the time by pointing to the figures on the dial. At present there are always two, the hour and minute hands and frequently a seconds hand also. Clocks at first were made with only the hour hand; the minute hand was introduced when the use of the pendulum made timekeeping sufficiently accurate for the indication of such small divisions.

Hanging Barrel—A going-barrel with its arbor supported only at the upper end.

Harris, Richard—An English clockmaker for whom it is claimed that he made the first pendulum clock—set up at St. Paul's, Covent Garden, in 1641. Most authorities agree, however, that this honor belongs to Huyghens.

Harrison, John—An English mechanician born at Faulby in Yorkshire in 1693. He made many improvements in the mechanism of clocks, the greatest of which was the compound pendulum. He won in 1761 a reward offered by Parliament in 1714 for an instrument that would determine longitude within thirty marine miles. Harrison's chronometer gave it within eighteen miles. He invented the going fusee, the gridiron compensation pendulum and suggested the idea for the compensation balance, afterward worked out by other watchmakers. Died 1776.

Hautefeuille, John—(Abbe.) Born 1647. Died 1724. He disputed successfully Huyghens' claim to a prior invention of the steel balance spring. He is also credited with the invention about 1722 of the rack-lever escapement.

Heart-Piece—The heart-shaped cam on the center-seconds wheel of a chronograph, which causes the hand to fly back to zero.

Hele, Peter—(See Henlein, Peter.) Some historians credit invention of first watch to Peter Hele. There is no doubt, however, that Hele and Henlein were one and the same. Preponderance of authority favors "Henlein" as the correct spelling of the name.

Helical—Following the course of a helix or spiral.

Heliotropion—See "Polos."

Hemicycle—Form of sun-dial in which the shadow of a vertical pointer or "gnomon" is cast upon and moves around the inner surface of a half globe or sphere. Supposed to have been invented about 350 B. C. (See Sun-Dial). Vitruvius, the Roman Engineer, ascribes invention to the Babylonian priest and astronomer, Berosus.

Henlein, Peter—Sometimes called Peter Hele. A clockmaker of Nuremberg, who is believed to have made the first portable (pocket) clock or watch sometime early in the sixteenth century. Born 1480. Died about 1540. His clock was round, driven by a spring and had small wheels of steel. It was much larger than present day watches.

Hollow Pinion—A pinion bored through the center. The center pinion in many watches is hollow.

"Hon-Woo-Et-Low" or Copper Jars Dropping Water—A form of clepsydra at Canton, China, said to be between 3000 and 4000 years old. It consists of four copper jars arranged on steps. Each jar drops water into the one below it until the last one, in which a bamboo float, indicates the time in a rude way.

Hooke, Robert, M. D.—An English physician-philosopher born on the Isle of Wight in 1635. His accomplishments were numerous. He claimed to have discovered the isochronism of the balance spring and its application to watches, though this was also claimed by Huyghens. He invented a pendulum timekeeper for finding the longitude at sea; devised the first wheel-cutting engine about 1670; and he invented the anchor escapement for clocks. His studies and inventions covered a wide field. He died in 1702.

Horologe, (Orologe), (Horologium)—A general term applied indiscriminately in old writings to any mechanism for measuring time.

Horological Institute—British—An association of watchmakers founded in 1858 for the purpose of advancing the horological arts.

Horological Periodicals, American—American Jeweler, (Monthly), Chicago, Ill.; Goldsmith and Silversmith, (Monthly), New Haven, Conn.; Jeweler's Circular, (Weekly), New York,; Keystone (Monthly), Philadelphia, Pa.; Manufacturing Jeweler, Providence, R. I.; Mid-Continent Jeweler, Kansas City, Mo.; National Jeweler, (Monthly), Chicago, Ill.; Northwestern Jeweler, St. Paul, Minn.; Pacific Goldsmith, (Monthly), San Francisco, Cal.; Trader and Canadian Jeweler, Toronto, Canada.

Horologium—See Horologe.

Horology-The science of time-measurement or of the construction of time pieces.

Hour—Now consisting of sixty minutes or one twenty-fourth of an equinoctial day. Formerly one twelfth of the time between sunrise and sunset, and one twelfth of the time between sunset and sunrise; hence of different lengths for day and night in the different seasons. This required much adjustment of clocks; and automatic devices for such adjustment were in great demand. A standard hour of uniform length for all times and seasons was not adopted in Paris—the last place to change—until 1816.

Hour-Glass—A device for measuring hours. It has two cone-shaped superimposed glass globes connected at their apexes through a small opening. The glass contains just that quantity of sand, or mercury, as will flow in one hour through the opening from the upper globe to the lower. When it has run through the glass is reversed. See: Sand Glass. Like the sun-dial and the clepsydra, the hour-glass is older than we know. Its use probably followed close upon that of the clepsydra, or may even have preceded it in dry countries like Egypt and Babylonia, where sand was all about and water was not a thing to waste. Of its original forms there is no authentic record. Dry sand does not, like water, run faster or slower through a given opening according to the pressure from above; its rate is the same whether the upper glass is full or nearly empty. Also the hour-glass never needs to be refilled, but only to be reversed, and the same sand used over and over again. On the other hand, its convenience diminished as its size increased. It was too clumsy for use if made large enough to run without attention for more than an hour or two; and in so large a glass there was more danger that the sand, however dry, might cake up and stop running. It must somehow have been transparent for convenient reading, because sand can register the time only by its flow: it cannot be made to raise a float or work a pointer. But the Egyptians very early learned to manufacture glass, and there were other substances. A legend ascribes the invention of the sand-glass to Luitprand, a Carthusian monk of the Eighth Century A. D. But this, if there is any truth in the story at all, must have been some improvement or reinvention after the forgetfulness of the Dark Ages. The device is plainly shown in Greek sculptures antedating the Christian era. Nowadays the sand-glass has pretty much disappeared, except as a kitchen timepiece for boiling eggs and the like.

Hour Hand—The hand of a watch or clock which indicates the hour: for long after clocks were first made, the only hand provided.

Hour Wheel—The wheel which revolves on the minute wheel or cannon pinion and carries the hour hand.

Howard, Edward—Born at Hingham, Mass., October 6, 1813. Having served a regular apprenticeship in clockmaking he entered into partnership with D. P. Davis, at the age of 29, to make clocks. He was a clever mechanic and invented many pieces of mechanism, among them the swing rest. In 1849 he and Davis with A. L. Dennison and others organized the American Horologe Company for the manufacture of watches by machinery, and with the parts interchangeable—the American principle of today. Though they were not financially successful the American watch industry owes its present day success largely to this beginning by Edward Howard and Aaron L. Dennison. The first company developed into the present Waltham Company, and later Mr. Howard established the E. Howard Co., at Roxbury, but severed his connection with them in 1882 and retired from business. He died March 5, 1904.

Huggeford, Ignatius—An English watchmaker, one of whose watches was used to defraud Facio of his patent on the use of jewels in watches. See Facio, Nicolas.

Hunter, or Hunting-Case—A watch case which has a solid metal cover over the dial.

Hunter, George—Identified with watchmaking in America since about 1860—in the Waltham and Elgin Companies. He was general superintendent of the latter from 1872 to 1903, after which he was made consulting superintendent.

Huyghens, Christian—A celebrated Dutch astronomer and mathematician born at The Hague, April 14, 1629. Although the honor is claimed for Richard Harris in 1641 and for Vincent Galileo in 1649 it seems historically established that Huyghens in 1657 was the first to apply to clocks the theory of the isochronism of the pendulum which the great Galileo had discovered. In 1669 he published his important work, "Horologium Oscillatorium." In 1673 he made the first clock with concentric hour and minute hands. He died in 1695.

Huyghens' Checks—The arc of a swinging pendulum is a segment of a circle. For perfect isochronism it should be a cycloidal segment. To accomplish this Huyghens fixed curved brass pieces called checks for the cord to strike against but he caused thereby a greater error than he remedied. This end was later accomplished by suspending the pendulum by means of a flat steel strip instead of a cord; a device credited to Robert Hooke.

Hypocycloid—A curve generated by any point in the circumference of a circle which is rolled on the inner side of the circumference of a larger fixed circle.

Idler, Idle Wheel, or Intermediate Wheel—A toothed wheel used to connect driver and follower wheels so that both shall rotate in the same direction.

Impulse—The push transmitted to the pallet by the escape wheel.

Impulse Pin—The jewel pin—usually a ruby—on the table roller of the lever escapement, which playing into the fork of the lever transmits the impulse to the balance.

Independent Center-Seconds—A watch peculiarly adapted to the use of the medical profession. It carries on a separate train a long seconds hand in addition to the hands of the ordinary watch which can be stopped without stopping the watch.

Independent Seconds—A watch whose seconds hand is driven by a separate train.

Ingersoll, Charles Henry—Secretary, Treasurer and General Manager of Robt. H. Ingersoll & Brothers., watch manufacturers, of New York City. Born at Delta, Eaton County, Michigan, October 29, 1865, a son of Orville Boudinot and Mary Elizabeth (Beers) Ingersoll. At the early age of fifteen years he left home and went to New York City, where he entered the employ of his brother, Robert H., who was then engaged in the business of manufacturing rubber stamps. Since 1880 he has been continuously associated with his brother in various business enterprises and in the direction and management of the Ingersoll organization. Married Eleanor Ramsey Bond of Brooklyn, New York, July 5, 1898. Residence, South Orange, New Jersey.

Ingersoll, Robert Hawley—Founder and President of Robt. H. Ingersoll & Brothers., watch manufacturers, of New York City. Born December 26, 1859, of Orville Boudinot and Mary Elizabeth (Beers) Ingersoll, at Delta, Eaton County, Michigan, he received his early education in the public schools of his native town. In 1879, at the age of nineteen years, he came to New York City, and in the following year engaged in the business of manufacturing rubber stamps; later, he established a mail order business, selling various "dollar" specialties and novelties. While engaged in this business he conceived the idea and in 1892 commenced the manufacture of the "dollar watch," since which time over 50,000,000 watches have been produced and sold by the Ingersoll organization. Married June 20, 1904, to Roberta Marie Bannister of Green Bay, Wisconsin. Residence, Oyster Bay, Long Island.

Ingersoll, William Harrison—Marketing Manager of Robert H. Ingersoll & Brothers., watch manufacturers, New York City. Born March 22, 1879, near Lansing, Michigan. He received a grammar and high school education and three years' technical training for electrical engineer. In 1901 he entered business in the retail sporting goods store of Robt. H. Ingersoll & Brothers. in New York City and was soon placed in charge of the Ingersoll watch advertising, over which he exercised close supervision ever since, except for two periods prior to 1908, when he sought and gained valuable outside experience in other capacities, such as salesman and as manager of the Ingersoll watch business in Canada; he then became advertising manager, later sales and advertising manager and then general marketing manager for developing all markets of all countries of the world for the Ingersoll products. Active in the promotion of advertising research, Mr. Ingersoll was one of the founders of Truth in Advertising work, assisted in establishing a Fellowship in Advertising Research at Columbia University, New York City, and has written and lectured extensively on salesmanship, advertising, marketing and related subjects. His residence is at Maplewood, New Jersey.

Ingold, Franz—A Swiss watchmaker who had the idea of making watch parts on the interchangeable plan long before it was put into practice anywhere. He was ill-received by labor and capital alike when he presented his plans in France, England, and America. In England he was nearly mobbed. In 1842-43 he obtained patents on some machinery in this line, but the machines were clumsy and for the most part impracticable. There has been a tendency to credit Ingold as the source of Dennison's ideas on this subject, though Dennison says he never heard of Ingold until after he had started manufacturing.

Intercalary—Introduced or added arbitrarily to a calendar; for example, the 29th day of February is an intercalary day.

Interchangeability—America's greatest contribution to watchmaking has been the standardizing of parts and the manufacturing of each of them, exactly alike, in great quantities. So that repairing an American watch is largely a matter of obtaining a new part similar to the damaged one, and simply putting it in place.

Invar—An alloy of nickel and steel claimed to be non-magnetizable. Used for certain parts of watches at the time when non-magnetizable watches were desirable. Invar is practically non-expansible when the nickel in it is about 37%.

Isochronism—That property of a pendulum or balance spring by virtue of which its vibrations, of whatever length, are all made in exactly equal periods of time.

Jacks; or Jack o' the Clock—Figures on the old turret clocks which automatically struck the hours. They preceded dials tho were usually left when the dials were added. There are Jacks on the clock at St. Mary Steps, Exeter; Norwich Cathedral, South Aisle; and St. Dunstan's in Fleet St., among others.

Jacquemarts—Figures of man and woman which struck the hours on the clock set up by Philip of Burgundy at Dijon, prior to 1370. G. Peignot says they are so named from Jacquemart, a clock maker of Lille, employed by the Duke of Burgundy in 1442. The lack of co-ordination in the dates tends to controvert the claim.

Jerome, Chauncey—Originator of the one-day brass clock movement which enormously increased the American clock business and opened a market for American clocks in Europe. Born in Canaan, Connecticut, in 1793. Established the Jerome Clock Company at New Haven, Connecticut. This was the predecessor of The New Haven Clock Company.

Jewelled—Fitted with precious stones to diminish wear as distinguished from precious stones for ornament. In the best watches ruby and sapphire are used. In lower grade watches quartz, amethyst and garnet.

Jewels—Used in watches as bushings at the ends of pivots and in other places which sustain much wear. They:

• 1. Provide smooth bearings for the pivots.
• 2. Obviate corrosion.
• 3. Reduce the wear from abrasion.

Sapphire is the best of the jewels in use and ruby second. Chrysolite is also used and garnet, tho the latter is too brittle for most service. This use of jewels was invented by Nicolas Facio—a Swiss watchmaker about 1705.

Julian Period—A period of 7980 years obtained by multiplying 28, 19 and 15—the numbers representing the cycles of the sun and moon, and the Roman Indiction. It will end 3267 A. D., until which time there cannot be two years having the same numbers for three cycles.

Jura Mountains—A watchmaking center in Switzerland. The industry grew rapidly following the success of Daniel Jean Richard in 1679. This section is the center of the system of watch-manufacturing most nearly like the American system. See Geneva.

Jurgensen, Jules—One of the most famous watchmakers of the 19th century; a son of Urban Jurgensen, born in 1808. He studied physics, mechanics and astronomy in Paris and London and finally settled in Locle, Switzerland, specializing in pocket chronometers, which have become famous as the Jurgensen watches. He died in 1877; and was succeeded by his son, Jules F. U. Jurgensen.

Jurgensen, Urban—A Danish mathematician and watchmaker born in 1776. He practiced his trade for a time in Switzerland, worked in Paris under Breguet and Berthoud, and then in London, before returning to Copenhagen to enter into partnership with his father, the court watchmaker. He was made superintendent of all the chronometers of the Danish navy and received several decorations. He died in 1830.

Kew Observatory—The central meteorological observatory of the United Kingdom. Established at Richmond in 1842 and afterward transferred to the Royal Society. Since 1900 it has been a department of the National Laboratory. Important to the watch business because of the famous Kew tests of timekeepers and awards for accuracy of performance.

Keyless Watches—Watches winding without a key. Such watches were made as early as 1686 but did not come into general use until 1843, when Adrien Phillipe (Geneva) introduced the "shifting clutch" type, and when the "rocking bar" mechanism was introduced in 1855. These are the types in use today. Self-winding watches have been made from time to time. Napoleon is said to have had one which wound automatically from the motion of being carried. The abandonment of the key nullified the usefulness of the fusee, although some keyless fusee movements were attempted.

Knuckles—The rounded parts of a watchcase that form the hinges or joints. Usually two on the cover.

La Chaux de Fonds—A watchmaking center in Switzerland which, in 1840, with a population of 9678, had 3109 watchmakers. At present it is the leading exporter of gold watches in Switzerland. In this section the system of manufacturing is much like the American system.

Laminated—Made up of tin sheets of beaten, rolled or pressed metal. In the compensation balance—the sheets are of brass and steel, or brass and aluminum.

Lancaster, Pa.—A town where there have been watch factories for upwards of fifty years.

Lange, Adolph—An eminent Dresden watchmaker born there in 1815, famous for his astronomical clocks, chronometers, and fine watches. Under the direction and with the assistance of his government he established the extensive watchmaking industry of Glashutte. He died in 1875.

Lantern Pinion—A pinion consisting of two circular metal end plates usually of brass joined by short steel wires which act as cogs in a gear.

Latitude—1. In astronomy, the angular elevation of a heavenly body above the ecliptic. 2. In geography a distance measured in degrees, minutes and seconds north or south from the equator. 3. In dial work, the elevation of the pole of the heavens; the angle at which the plane of the horizon is cut by the earth's axis.

Lead—The continuous action of a wheel tooth which impels the leaf of a pinion or the pallet of a balance.

Leap-Year—See Calendar, Gregorian.

Leaves—The name applied to the teeth of a pinion wheel.

Lepaute, J. A.—1709-1789. A French clockmaker famous for his turret clocks; the inventor of the pin-wheel escapement and an authoritative writer on horological subjects. He wrote "TraitÉ d'Horlogerie" which was afterward revised and added to by Lalaude.

Lepire, Jean Antoine—Born 1720. Died 1814. A celebrated watchmaker of Paris in the 18th century. About 1770 he introduced bars to take the place of a top plate, omitted the fusee, used a cylinder escapement and supported his mainspring barrel arbor at one end only. He attempted to establish a watch factory for Voltaire at Ferney but with no success. He is sometimes credited with making the first thin watch.

Le Roy, Julien—1686-1759. A French scientist and watchmaker. He invented the horizontal movement for turret clocks, a form of repeating mechanism. He constructed the first compensation balance.

Le Roy, Pierre—1717-1785. Son of Julien Le Roy. Esteemed the greatest of all French horologists. He invented a form of duplex escapement and an escapement which formed the basis for the present chronometer escapement.

Lever—That part of a lever escapement to which are attached the pallet arms, and which thus transmits motion from the escape wheel to the balance.

Lift, or Lifting Arc—That portion of the oscillation of a balance during which it received its impulse. The remainder of the turn is called the supplementary arc.

Lightfoot, Peter—A Glastonbury monk, maker of the Glastonbury and Wimburne clocks, 1335.

Lips—In a cylinder escapement, the rounded edges of the cylinder through which the escape wheel gives impulse to the balance.

Locking—1. The stopping of the escape wheel of a watch or clock. 2. The portion of the pallet on which the teeth of the escape wheel drop. 3. The depth to which the escape tooth laps upon the pallet at the moment it leaves the impulse face.

Logan, John—Born in Lowell, Mass., 1844. Invented a new method of tempering springs and made superior main and balance springs. He was connected for several years with the Waltham Watch Company, during which time he invented many labor-saving machines. Died 1893.

Longitude—The circular distance east or west subtending the angle which two meridional planes make at the axis of the earth, one of them being a standard reference meridian.

Longines—A watch factory at St. Imier in the Jura Mountains, near La Chaux de Fonds, established in 1874. Here all parts are made under one roof and the work is done by machinery.

Lower Plate—The plate in a watch nearest the dial. Also called the "dial plate." It carries the lower pivots of the movement.

Luitprand—A monk of Chartres who revived the art of glass-blowing at the end of the 8th century. To him is sometimes ascribed the invention of the sand-glass.

Luminous Dial—A watch dial whose hands and figures are so treated as to be visible in the dark. Formerly accomplished by a phosphorescent paint which required frequent exposure to sunlight to be effective and retained its luminosity only an hour or two. Now effected by means of a compound absolutely independent of the sunlight and of a lasting glow. See Radiolite.

Lunette—The usual form of rounded watch crystal.

Mainspring—The long steel ribbon used for driving a clock or watch. The spring is coiled into a circular metal box called the barrel and the outer end of the spring is fastened to the barrel; the inner end to the arbor of the great wheel. First applied, replacing weights, by Peter Henlein of Nuremberg, about 1500.

Maintaining Power—The device for driving the train while a watch or clock is being wound.

Marsh, E. A.—An important figure in watch manufacturing in America for a number of years. Born at Sunderland, Conn., in 1837, in 1863 he entered the employ of the Waltham Watch Company and rose to the position of General Superintendent. In 1908 he retired from active service but retains his connection with the company as consulting superintendent. Besides his practical services to the watchmaking industry Mr. Marsh wrote "The Evolution of Automat Machinery," in 1896.

Massey, Edward—An English watchmaker of the early nineteenth century. He invented the "crank roller" escapement, a kind of keyless winding for watches, and many other watch parts.

Mean Solar Day—The average length of all the solar days in a year. This period is divided into 24 parts, or hours.

Mean Time—Clocks, watches, etc., are made to measure equal units of time instead of the apparent time indicated by the sun. Mean time and true solar time agree only four times in a year. See Equation of Time.

Mercer's Balance-A balance of the ordinary kind fitted with an auxiliary—a laminated arm of brass and steel fixed at one end to the central bar of the balance and on its free end carrying two adjustable screws. This auxiliary may be arranged for either extreme of temperature with great accuracy.

Meridian Dial—A dial for determining when the sun is on the meridian. It is very simply constructed. For directions see "Watch and Clockmakers' Handbook," by F. J. Britten.

Meridian Watch—A watch which shows the time in a number of places in different parts of the world. It is set to Greenwich time and marks the difference between this and the time of all the great metropolitan cities in both hemispheres.

Metronome—An instrument for indicating and marking exact time music. It consists of a counterbalanced, or reversed, pendulum, which may be regulated to swing at any desired number of vibrations per minute.

Middle Temperature Error—The compensation balance does not exactly meet the temperature error. The rim expands too much with decrease of temperature and contracts too little with the increase. Hence a watch or chronometer can be correctly adjusted for two points only. The unavoidable error between is the middle temperature error.

Minute—The sixtieth part of a mean solar hour.

Minute Hand—The hand on a clock or watch which indicates the minutes. In the earlier days clocks had no minute hand. It was first concentered with the hour hand in 1673.

Minute Wheel—The wheel which carries the minute hand and is driven by the cannon pinion.

Minute Wheel Pin or Stud—The stud fixed to the plate on which the minute wheel pinion turns.

Minute Wheel Pinion or "Nut"—The pinion in watches on which the minute wheel is mounted and which drives the hour wheel.

Moment of Inertia—The resistance of a body in motion (or at rest) to a change in the velocity or direction of its motion. In a rotating body the sum of the products formed by multiplying the mass of each particle by the square of its distance from an axis.

Month—An arbitrary division of the year, varying in the number of days it contains, according to the calendar in use. See Calendar.

Mortise—A slot or hole into which a tenon of corresponding shape is to be fitted.

Moseley, C. S.—A pioneer in the field of designing and building automatic watchmaking machinery. He invented some of the most delicate and complicated tools and mechanisms used in watch manufacture. He was early connected with the Waltham Co., master mechanic for the Nashua Co., during its brief history; and later general superintendent of the Elgin National Watch Company.

Motion—The wheels that carry the hands: cannon pinion, horn wheel and minute wheel and pinion.

Motion Work—The wheels in a watch which make the motion of the hour hand one twelfth as rapid as that of the minute hand.

Movement—The watch or clock complete, without dial or case—the mechanism of the watch or clock.

Mudge, Thomas—An English watchmaker of the 18th century. Born at Exeter in 1716, died 1794. In 1793 he received from Parliament three thousand pounds as a recompense for his improvements in chronometers. His work was celebrated for its excellence.

Name Bar—The bar which carries the upper end of the arbor of a watch barrel.

Naval Observatory—The United States Naval Observatory at Washington, D. C. There is there a superlatively accurate clock from which the time is flashed electrically to all parts of the United States.

Neuchatel—A town in the Jura Mountains' watch manufacturing district of Switzerland. A Cantonal Observatory at Neuchatel helps establish the reputation for the accuracy of Swiss watches.

Non-Magnetic Watch—A watch in which the quick-moving parts—lever, pallets, balance spring, etc., are made of some other metal besides steel—as aluminum bronze, invar, etc.

Nuremberg—A German city where Peter Henlein made the first watch. It was one of the chief clock centers of the 16th and 17th centuries and with Augsburg and Ulm supplied the markets of Europe with the first small clocks.

Nuremberg Eggs—Watches made in Nuremberg in the shape of eggs. If not the first watches at least very early examples.

Obelisk—A square shaft with a pyramidal top. The ancient Egyptian obelisks are thought to have served as gnomons.

Ogive—A pointed arch—of the architectural type known as Gothic.

Oil Sink—The cavity around the pivot hole in watch and clock plates, designed to hold a small particle of oil in contact with the pivot.

Ormolu—Gilt or bronzed metallic ware, or a fine bronze which has the appearance of being gilded. Used for ornamenting the cases of fine old clocks.

Orologe—An obsolete form of horologe. See Horologe.

Orologiers—An obsolete form of horologers, a term not now in use but signifying men who constructed time-pieces.

Orrery—A planetarium; an instrument showing the relative motions, positions and masses of the sun and planets. It was so named from Lord Orrery, for whom the first modern planetarium was made in England.

Oscillation—The movement back and forward of a pendulum or the swing of a balance spring. The vibration.

Overbanking—Pushing of the ruby pin past the lever, caused by excessive vibration of the balance. In a cylinder escapement the turning back of the cylinder until an escape wheel tooth catches and holds it. In a chronometer escapement the second unlocking of the escape wheel from the same cause.

Overcoil—The outermost coil of a Breguet spring which is bent back across the coil toward the center.

Pacificus—Archdeacon of Verona, died about 850 A.D. It is claimed by some that he made a clock furnished with an escapement. (Bailly.) But this is not proved, and others believe it to have been merely a water-clock.

Pad—The pallet of the anchor escapement for clocks.

Pair Case—At one time watches were made with two or even three separate cases. The outer one of shagreen tortoise shell, or some other ornamental material was sometimes for the protection of the delicate enamel on the inner case. Sometimes as in the case of repeaters the inner case was pierced to emit the sound. Then the outer one served as dust protection to the works.

Palladium—A soft metal formerly used in alloy with copper and silver for the balance and balance spring of non-magnetizable watches. Too soft to be as serviceable as steel, it has been superseded by a platinum alloy.

Pallet—Has different meanings, even among watchmakers. Generally, the part through which the escape wheel gives impulse to the balance or pendulum.

Pallet Staff—The arbor on which the pallet is mounted, and on which it turns.

Pallet Stone—The jewel on the contact face of the pallet, where it is struck by the teeth of the escape wheel.

Parallax—The apparent angular displacement of a heavenly body due to a change of the observer's position.

Pedometer—An instrument which registers the number of paces walked—hence if properly adjusted to the length of step of the wearer it gives the distance traversed.

Pendant—The small neck and knob of metal connecting the bow of a watch case with the band of the case.

Pendulum—A body suspended by a rod or cord and free to swing to and fro; used in clocks to regulate the velocity with which the driving power moves the wheels and hence the hands. The isochronism of a pendulum vibrating in a cycloidal arc was first discovered by Galileo but he did not apply it to clocks. Most authorities credit Christian Huyghens with that adaptation to instruments for keeping time. The pendulum was first suspended by a silk cord and thus vibrated in a circular instead of cycloidal arc. "Huyghens' Checks" were an unsuccessful attempt to remedy this. Dr. Hooke succeeded in remedying it by suspending the pendulum by a flat ribbon of spring steel.

Pendulum, Gridiron—Invented by Harrison in 1726, and still with slight improvements an effective timekeeper. The rod of this pendulum is constructed of five steel and four brass rods so arranged that those which expand most are counteracted by those of less expansion, and the length of the pendulum remains constant.

Pendulum, Mercurial Compensation—A pendulum having for a bob a jar of mercury which expands upward with the increase of temperature thus counteracting the lengthening of the rod from the same cause. Invented by Graham about 1720. With slight improvements still in use and keeps time very accurately.

Pendulum, Torsion—A pendulum vibrating by the alternate twisting and untwisting of an elastic suspension. The body is a horizontal disc weighted around its edges, and its suspension a steel or brass wire. The period of a torsion pendulum being much longer than a vibrating pendulum of the same length, the time of running is longer. Clocks fitted with torsion pendulums have run a year on one winding.

Pendulum Swing—The short ribbon of spring steel which suspends the pendulum of a clock.

Penetration of Gearing—The depth of intermeshing of the teeth of pinion and wheel.

Phillips Spring—A balance spring with terminal curves after rules laid down by M. Phillips, an eminent French mathematician. A term seldom used though his curves are generally followed.

Pillar—The three or four short brass posts which keep the plates at their proper distance apart. In early days made in very artistic and elaborate shapes. Later they became plain straight cylindrical columns.

Pillar Model—A type of movement in which the works are hung between two plates supported and separated by posts or pillars and forming all the principal bearings of the movement. Only average adjustment is possible in this model. In this model the plate is sometimes cut away to imitate a "bridge model." The opposite extreme in construction to the "bridge model."

Pillar Plate—The lower plate of a watch movement—the one nearest the dial—to which the pillars are solidly fixed, in a "pillar model."

Pinchbeck, or "Pinchbeck Gold"—An alloy of three parts zinc to four of copper which "resembles gold in color, smell and ductility." So called from its inventor Christopher Pinchbeck (1670-1732) who during his life guarded the secret of its composition very jealously.

Pinion—The smaller of two toothed wheels that work together. The teeth of a pinion are called leaves. See also Lantern Pinion.

Pinion, Lantern—A pinion consisting of two circular metal plates joined by short steel wires.

Pitch—The length of the arc of the circumference of the pitch circle from center to center of two adjacent teeth.

Pitch Circle—The geometrical circle traced with the center of the wheel as its center and at which the curved tips of the teeth begin. The diameter is proportional to the number of teeth determined upon. The proportion of the pitch circles of a wheel and a pinion gearing together is determined by the ratio of revolutions desired.

Pitkin, Henry—With his brother, James F., he started at Hartford, Conn., in 1838, the first factory for machine-made watches in the United States. They made their own machinery, which was very crude. After making about 800 watches they were forced to abandon the project, being unable to compete with cheap foreign watches. He died in 1845.

Pivots—The ends of the rotating arbors in a watch that run in bearings.

Planetarium—An astronomical clock which exhibits the relative motions and positions of the members of the solar system. Has no regulating system and usually no driving power but is run by turning a crank by hand.

Plates—In watches and small clocks the circular discs of brass to which the mechanism of the watch is supported. In large clocks the plates are usually square-cornered oblong. See Pillar Plate, Top Plate, Half Plate, Full Plate, etc. In half-plate, and three-quarter-plate types of watches part of the disc is cut away.

Pocket Chronometer—A watch with a chronometer escapement.

Polos—A basin in the center of which the perpendicular staff or gnomon was erected, and marked by lines for the twelve portions of the sun-lit day. Herodotus ascribes its invention to the Babylonians, Phavorinus claims it for Anaximander and Pliny for Anaximenes. Also called "Heliotropion."

Potance or Potence—A vertical or hang down bracket, supporting the lower end of the balance staff in full-plate watches.

Prescot—A town in a remote part of Lancashire for years the center of the movement trade in England.

Push Piece—1. The milled knob pushed in from the pendant to open the case. 2. The boss pushed in when the watch is to be set.

Quare, Daniel—1649-1724—Claimed the invention of the repeater, and backed by the Clockmakers' Company obtained the patent against Barlow from James II. Also credited with the invention of equation clocks. He was master of the Clockmakers' Company in 1708. He first used the concentred minute hand in England, but Huyghens had preceded him in this in the Netherlands.

Quarter—1. A term in common use for the period of three months—a quarter of the year. 2. The fourth part of an hour—15 minutes.

Quick Train—A watch movement balance vibrates 18,000 times per hour. Unequal mainspring pull is less felt in the quick train. Used generally in Switzerland and America, and a feature of practically all modern watches.

Rack—A straight bar, or segment of a circle, with teeth along one edge. It has a reciprocating motion.

"Radiolite"—Trade name adopted by Robt. H. Ingersoll & Brothers. for their watches having black faced dials with luminous hands and numerals. Composed of a substance in which genuine radium is used in minute proportions.

Radius of Gyration—The distance from the center of gyration to the axis of rotation.

Ramsey, Davis—One of the earliest British watchmakers of renown. He was appointed "keeper of clocks and watches" to James I, and appears to have retained his appointments after the death of the latter. He was the first master of the Clockmakers' Company tho he seems to have taken little active part in the management thereof. Scott introduces him into his story—"The Fortunes of Nigel" as a Keeper of a shop a few yards east of Temple Bar. Without doubt he was the leading clockmaker of his day. He died in 1655.

Ratchet—The pawl, or dog, which engages in the teeth of a ratchet wheel and prevents it from turning backward. It is held lightly against the periphery of the ratchet wheel by a small spring known as the ratchet spring.

Ratchet Wheel—A wheel with triangular teeth fixed on to an arbor to prevent the latter from turning backward. The fronts of the teeth are radial, the backs straight lines running from the tip of one tooth to the base of the next. In going-barrel, keyless watches the ratchet has epicycloidal teeth. By "the ratchet" in a watch, chronometer or clock with mainspring is meant the ratchet fastened to the barrel arbor to prevent the mainspring from slipping back when it is being wound.

Recoil—In recoil escapements the pallets not only stop the escape wheel but actually turn it backward a slight distance. This backward motion is called the recoil.

Regulator—1. A standard clock with compensated pendulum with which less accurate movements are compared. 2. The lever in a watch by which the curb-pins regulating the swing of the hairspring are shifted.

Remontoire—An arrangement in the upper part of the going train by which a weak spring is wound up or a small weight is lifted that gives impulse to the escape wheel at short intervals. Its use is to counteract the irregularities in impulse due to the coarse train, etc. They are delicate and complicated and now superseded by the Double Three-legged Gravity Escapement.

Repeater—A striking watch or clock which by the pulling of a string or the pressing of a button could be made to repeat the last hour and part hour, struck. In vogue during the 18th century. Credit for the invention was disputed by Daniel Quare and Edward Barlow. James II gave the decision in favor of Quare whose mechanism was a trifle simpler.

Repousse—A kind of chasing in which the metal is punched or pressed from the back bringing the design into higher relief than by the usual method of indenting.

Ring-Dial—See Sun-dial, Portable.

Richard, Daniel Jean—A Swiss watchmaker, born at La Sagne in 1665. At fifteen a watch having come into his hands, he constructed a similar one unaided. That was the first watch made in Neuchatel. After a time in Geneva he set up business in La Sagne, afterwards moving to Locle. He created the watch industry of Neuchatel and saw it grow to a neighborhood of five hundred workers. He died at Locle 1741. In 1888 a bronze statue was erected to him there.

Robbins, Royal E.—Born in Connecticut 1824. He was essentially one of the "fathers" of American watchmaking because it was through his financing and clever management that the first watch company finally succeeded in making a financial success.

Roller—The circular plate in a lever escapement, into which the ruby pin is set.

Roller-Jewel—Same as "impulse pin."

Roman Indiction—A period of fifteen years appointed by the Emperor Constantine 312 A. D. for the payment of certain taxes.

Rose Engine—A lathe in which the rotary movement of the mandrel is combined with a lateral, reciprocating movement of the tool rest; used for ornamenting the outside cases of watches with involved curved engraving.

Ruby Pin—The impulse pin in a lever escapement, made of a ruby.

Ruby Roller—The roller in a duplex escapement against which the teeth of the escape wheel are locked.

Run—In the lever escapement, the extent of the movement of the lever toward the banking pins after the "drop" on to the locking.

Sabinianus—Pope from 604 to 606. Said to have invented a clock in 612 A. D., but the clock he is supposed to have built was probably only another of many forms of clepsydrae, or water clocks.

Safety Pinion—A center pinion in a going-barrel watch which allows the recoil of the barrel if the mainspring breaks.

Sand-Glass—(Clepsammia)—A dumb-bell-shaped glass globe containing sand, and with a small aperture through which the sand flows in a certain fixed time. The most common form is the hour-glass but many others are in use as the three-minute glass for boiling eggs, the two-minute glass used by the British Parliament, etc. Dried and finely powdered eggshell sometimes used in place of sand. The principle is the same as that of the simplest form of clepsydra. See Hour-Glass.

Sandoz and Trot—A firm which established the first watch factory in Switzerland in 1804. Previous to that time watchmaking had been a house industry.

Second—One-sixtieth of a minute: 1-3600 of a mean solar hour.

Secondary Compensation—Same as "auxiliary compensation." See Auxiliary.

Seconds Hand—The hand on the dial of a clock or watch which revolves once a minute. Sometimes small and set in a small circle of its own. Sometimes long and traverses the whole dial. See Center-seconds and Sweep-seconds.

Seconds Pivot—The prolongation of the fourth wheel arbor to which the seconds hand of a watch is fixed.

Seconds, Split—Divided seconds—into quarters, or fifths; measured by a chronograph.

Shadow—A darkened space resulting from the interception of light by an opaque body.

Shagreen—Made from the tough skin that covers the crupper of a horse or ass. Rough seeds are trodden into the skin and then allowed to dry. The seeds are shaken out and the skin dyed green. Then the rough surface is rubbed down smooth leaving white spots on the green ground. Also made from the rough skin of sharks and dolphins. Formerly used a great deal for the outer cases of watches. See Pair Cases.

Sherwood, Napoleon Bonaparte—Born in 1823. About 1855 he entered the watchmaking business in the employ of the Waltham Watch Co. He revolutionized jeweling methods and invented among other things a "Counter-sinker," "End-shake tools," "Truing-up tools" and "Opener." In 1864 he organized the Newark Watch Company but within a few months severed his connection with it. He died in 1872.

Sidereal Time—The standard used by astronomers; measured by the diurnal rotation of the earth, which turns on its axis in 23 hours, 56 minutes, 4.1 seconds. The sidereal day is therefore 3 minutes, 56 seconds shorter than the mean solar day. Mean time clocks can be regulated with greater facility by the stars than by the sun for the motion of the earth with regard to the fixed stars is uniform. Clocks all over the United States are so regulated from the Naval Observatory at Washington.

Side-Shake—Freedom of pivots to move sideways. See End-Shake.

Slow Train—A train whose balance vibrates 14,400 times an hour. Now never used in pocket watches because of susceptibility to inequalities in the pull of the mainspring, jars, sudden movements, etc. Used, however, in marine chronometers.

Snail—A cam shaped like a snail, used generally for gradually lifting and suddenly discharging a lever, as in the striking mechanism of clocks.

Snailing—A method of ornamenting with circles and bars parts of a watch movement which it is not desirable to polish highly.

Solar Time—Time marked by the diurnal revolution of the earth with regard to the sun, of which the midday is the instant at which the sun appears at its greatest height above the horizon. This instant varies from twelve o'clock mean time because the earth also advances in its orbit and its meridians are not perpendicular to the ecliptic.

Spandrels—The corners of a square face outside the dial of a clock. Formerly very beautifully decorated. The age of the clock can be told approximately from the form of ornamentation employed.

Split Seconds—A chronograph in which there are two center-seconds hands—one under the other—which can be stopped independently of one another.

Spring-Clocks—Clocks whose driving power is a coiled spring instead of a weight.

Stackfreed—The derivation of the word is obscure; it is possibly Persian. A device to counteract the difference in power of the mainspring at the different stages of its unwinding. Fixed to the mainspring arbor above the top plate is a pinion having eight leaves, which gears with a wheel having twenty-four teeth, which do not quite fill out the circumference of the wheel. Fastened to the wheel is a cam, concentric for about seven-eighths of its circumference and indented for the remainder. Into a groove in the concentric portion of the edge is pressed a roller which is pivoted at the free end of a strong curved spring. When the mainspring is fully wound the roller rests in the curved depression of the cam and the effort required to lift the roller up the incline absorbs some of the mainspring's power. On the other hand when the mainspring is nearly run down, the roller is descending an inclined plane and absorbs less of the power. Not an acceptable device and now rarely met with.

Stem-Winding—The ordinary method of winding keyless watches by means of a stem running through the pendant.

Stop Work—An arrangement for preventing the overwinding of a mainspring or a clock weight.

Stratton, N. P.—One of the early watchmakers connected with American manufacture. He was an apprentice of the Pitkin Bros., and was sent by the Waltham Company to England in 1852 to learn gilding and etching. He was made assistant superintendent of the Waltham Co. in 1857. He invented a mainspring barrel and a hair-spring stud which were later adopted by the Waltham Company.

Striking-Work—The part of a clock's mechanism devoted to striking. The chief forms are Rack, and Locking-plate, or Count-wheel. See separate articles.

Striking-Work, Locking-Plate, or Count-Wheel—Used in turret clocks where there is no occasion for the repeating movement. This form of striking work does not allow of the repetition or omission of the striking of any hour without making the next one wrong.

Striking-Work—Rack—A form of striking work used largely in house clocks; the number of blows to be struck depends merely on the position of a wheel attached to the going part. In this form the striking of any horn may be omitted or repeated without deranging the following strikes.

Stud—1. A small piece of metal pierced to receive the outer or upper coil of a balance spring. 2. The holder of the fusee stop-work. 3. Any fixed holder used in a watch or clock, not otherwise named, is called a stud.

Style—The finger or gnomon on a sun-dial whose shadow, falling on the plate, indicates the time.

Sully, Henry—An English watchmaker of the early eighteenth century who lived most of his life in France. He presented the French Academy with a marine timekeeper superior to the timepieces of the period, and a memoir describing it. He died shortly afterward and advance in the art was delayed.

Sun-Dial—A device for telling time by the shadow of a style, cast by the sun, as thrown upon a disk or plate marked with the hour lines. Dials were named from their positions—equinoctial or equatorial; east; erect or vertical; horizontal; inclining, etc., or from their purpose or method of use, as portable, reflecting, etc., or as in the case of the ring-dial, from their form. The word is derived from the Latin dies. The style in the earliest dials was a vertical staff, but later it was found that reasonable accuracy could only be obtained by a style set parallel to the earth's axis—that is, inclined to the horizontal at the angle of latitude of the locality in which the dial was set.

Even before the first astronomical discoveries of the Babylonians, people had felt some need of a convenient device to mark and measure the passing of the time, especially the shorter divisions of recurring time, the time of day. Sunrise and sunset marked themselves by the horizon, but noon was harder to determine, and the points of mid-morning and mid-afternoon harder still. And with the knowledge of those regular movements in the heavens which determine time on earth, and with the closer division of the day into its hours, that need became a sheer necessity.

The obvious measure of the sun's movements was the moving shadow cast by the sun itself. And the earliest device for recording time was naturally the sun-dial. Its origin fades into the twilight of antiquity. Long before we know anything about him, primitive man measured the moving shadow of some tree. And it occurred to him to set up a post or pillar in some convenient place, and mark out the positions into which the shadow swung. The earliest sun-dials were of this pattern, with a vertical pointer of gnomon, and the hours marked upon the ground. And it is related of the early Greeks that they told the time individually by marking and measuring the length of their own shadows. But the measure of time by the length of a shadow is very irregular at best, because of the yearly motion of the sun. The shortest shadow of the day will indeed fall at noon. But that noon shadow will vary in length according as the sun's noon is high in Summer or low in Winter; and so the whole scale of lengths will be different for every day in the year. If a three foot shadow means mid-afternoon today, it will mean quite another time tomorrow. And for measuring by the direction of the shadow, the vertical gnomon is more irregular still. For the swing of the shadow would depend not only upon the sun's motion across the sky from East to West, but also upon his slant North and South along the sky. And this would change from day to day. The difficulty was to make a dial of which the shadow would move as regularly as the sun moves.

This the ancients accomplished in a very simple and ingenious way. The sun moves in the sky as it were upon the inner surface of a hollow globe or sphere. So they made the dial a little hemisphere, place with its hollow side up toward the sky as a bowl stands on a table. The pointer was placed above and to the South of this, on the side toward the sun; and the Time was marked by the shadow of the tip end of the pointer which was a little ball or bead. The path of this shadow across the bowl reproduced exactly on a small scale the path of the sun across the great bowl of the heavens. And it was then an easy matter to mark off the bowl into equal divisions which the shadow would cross at equal intervals of the day. Of course, the track of the shadow changed with the season of the year. But it moved always as the sun moved, and just as regularly, giving a true measure of the solar day.

The principle of this was applied in several interesting variations. The defect of the Hemicycle, as this hollow type of dial was called, was that it could not be read accurately for short intervals. A shadow moving only a few inches in the whole day must move so slowly that one could hardly see it move at all. To mark the minutes, it must move faster, just as the minute hand of your watch moves faster than the hour hand, and the second hand faster still. One cannot read seconds from the hour hand, however accurately it moves, because it moves so slowly. So the idea was applied by making the shadow move across a street or courtyard, down one side and across and up the other side, as the sun opposite went up and across and down the sky. Sometimes the place was partly roofed over, and a single beam of light admitted through a small hole at the South end. The resulting spot of light would then move in the same way. The long sunbeam or shadow moved faster, and so could be read at shorter intervals. The Hemicycle is not certainly known to have been invented until long after this, about B. C. 350. But the principle of it is so simple and so entirely such as would occur to an intelligent man still ignorant of its mathematical explanation, that we may not unreasonably suppose it to have been discovered by experiments long before.

The final improvement of the sundial was the discovery that by slanting the gnomon so that it pointed exactly toward the North Pole of the sky, the direction of its shadow could be made to show the solar time correctly. Since the sky is infinitely far away, the line of the gnomon would then lie parallel to the axis of the heavens. And the sun, moving parallel to the celestial Equator, would always move straight across the gnomon. In other words, he would practically revolve around its sloping edge. Therefore the North and South motion of the sun would be as it were along the edge of the gnomon, and would not influence the direction of the shadow at all. His East and West motion alone would govern the swing of the shadow; and the dial would keep true time with the sun for every day in the year. There was no longer any necessity for hollowing out the dial itself into the concave form; it might just as well be the more convenient flat surface, and this might be either vertical or horizontal, so long as the gnomon pointed straight to the Celestial Pole. All that was needed was to mark out on the dial the true direction in which the shadow fell for each hour of the day.

Just when or by whom the instrument was thus scientifically perfected is not known. The calculations necessary to the projection of the hour lines upon a flat surface could hardly have been performed before Greek times. The Greeks ascribed the invention of the sundial to Anaximander, in the sixth century B. C., but sundials of various types had been known in various parts of the world long before then. On the other hand, the Hemicycle remained the common form of the instrument all through the classic period and even afterwards. The Babylonians were quite capable of understanding the principle of the sloping gnomon. And once this was discovered, it would have been entirely practical to set up the new dial beside a Hemicycle or Clepsydra, and find the angles of the hour lines by experiment. These, once laid out correctly, would be determined once for all. Even at its best the sundial had certain very marked limitations. Scientifically constructed, it would keep accurate time according to the visible sun. But it could not be read accurately unless made inconveniently large. It was inaccurate when removed from its original latitude, or displaced from a true North and South position; so that in any portable form it became a very rough measure indeed. Moreover, it was of course entirely useless at night or in bad weather or in shadow. And finally, it was never absolutely exact under the most ideal conditions, because of what is known as the Equation of Time. The Earth does not, in fact, move around the sun at an absolutely regular rate of speed; it moves a trifle faster during certain parts of the year and slower at others. The sun therefore varies correspondingly his apparent speed along the Ecliptic, so that even from noon to noon the sun is not always precisely on time. He may be as much as fifteen minutes late or early, according to the season. And our modern days are measured according to the sun's average rate, so as to allow for this variation and keep every day exactly twenty-four hours long. This of course no sun-dial can possibly be made to do, since it must follow the actual sun.

The sun-dial has remained in use to the present day. It seems strange to think of a sun-dial being used as a standard for setting clocks and actually to regulate the running of trains. But these things were done in civilized Europe within the last half century. It was only when the railroad and the telegraph had made standard time at once necessary and easy to obtain that the sun-dial altogether lost its position of authority.

Sun-Dials, Descriptions—Classical sun-dials were of many forms. Vitruvius, the Roman engineer, mentions thirteen, some of them portable; and ascribes the invention of the Hemicycle to the Babylonian astronomer and priest, Berosus. There was a famous dial of this type at the base of Cleopatra's Needle in Egypt. It is now at the British Museum. And the Emperor Augustus, returning from his Egyptian wars, brought home to Rome an obelisk which he set up as the gnomon of a huge dial in the Campus Martius. At Athens there was the famous Tower of the Winds; octagonal in shape, with a weather vane above, and below around the tower, the hours and the winds, to each of which the Greeks gave a personality and a name. There is a curious bit of accidental poetry in the marking of the sun-dial in Greece. The Greek numerals, like the Roman, were simply the letters of their alphabet arranged in a certain order. The hot hours of the day from noon to four o'clock were those commonly devoted by the Greeks to rest and recreation. Reckoning the day from sunrise, this period ran from the sixth hour through the ninth. And the numeral letters for Six, Seven, Eight and Nine, which marked those hours upon the dial, spell out the Greek word ????, the imperative of the verb to live. The poet Lucian thus points the moral:

The shepherds of the Pyrenees still consult their pocket dials. And the Turk makes a sun-dial of his two hands by holding them up with the tips of the thumbs joined horizontally and the forefingers extended upward; so that the shadow of one forefinger falls toward the other and by its position roughly indicates the time. But even now, when it has nearly gone from practical use, the sun-dial, as an appropriate adornment of our public parks and our private gardens, is becoming increasingly fashionable in our own generation.

Sun-dials are common in almost all parts of the world, and not a few of them have in one way or another become famous. The largest is at Jaipur in India, and was erected about 1730. Its gnomon is ninety feet high and one hundred and forty-seven feet long. A flight of stone steps run up the slope of it, and at the top there is a sort of little watch-tower. And the shadow, which falls upon a great stone quadrant instead of upon a flat surface, moves at the rate of two and a half inches a minute. Another great dial is the so-called Calendar Stone of Mexico, which was made by the Aztec priests more than a hundred years before the Spaniards came. It weighs nearly fifty tons, and is not only a sun-dial but a representation of the zodiac and a diagram of the astronomical changes of the year: thus showing that the ancient Mexicans in their own way paralleled the astrology of the Babylonians on the other side of the world. Probably the most expensive and elaborate sun-dial ever built was the one set up in 1669 by King Charles II of England in front of the banqueting house at White Hall in London. It was in the form of a tall pyramid on which were two hundred and seventy-one different dials, giving not only the hour of the day but various astronomical and geographical indications as well. The place called Seven Dials in London takes its name from a tall pillar with sun-dials around its top which used to stand at the junction of seven streets radiating starwise from that spot as a center. The pillar was overthrown in 1773 by a party of vandals digging for buried treasure which they believed to have been hidden beneath its base. Extensive list, descriptions and illustrations, See Book of Sun-dials, Mrs. Alfred Gatty; Sun-dials and Roses, Mrs. Alice Morse Earle.

Sun-Dials, Greek—1. Diogenes asserts that the first Greek dial or gnomon was erected by Anaximander of Miletus. It was probably a vertical rod on a horizontal plane. This was two centuries after the Dial of Ahaz. 2. On the "Tower of the Winds" in Athens—a dial on each face.

Sun-Dial, Hollow—A form of sun-dial invented by the Chaldean Berosus. A hollow hemisphere with a bead at its center, whose shadow indicated the hour of the day.

Sun-Dial, Mottoes—On nearly all sun-dials both ancient and modern there there is inscribed a motto—usually of the moral significance of the passage of time.

Very ancient also, as well as equally common in modern times is the custom of placing upon the sun-dial some appropriate motto expressive of the mystery of Time. There are hundreds of such mottoes, ranging in sentiment from the old Roman one: Horas non numero nisi Serenas. "I number no hours but the fair ones," to the couplet of a modern poet:

And these two thoughts, expressed in many forms, represent fairly the tenor of most of them. There is a story of a lazy apprentice asking a motto for his dial, to whom his master sharply replied: "Begone about your business!" and the fellow, appropriately enough, took that for the motto required. It is at least a familiar sentiment, especially in Puritan times; and equally so during the Middle Ages is that more mystic suggestion, Umbra Dei—"the Shadow of God."

Sun-Dial, Portable—Made in different shapes and upon different plans small enough to carry about. The most common form was the ring dial, consisting of a metal ring with a hole in it through which the light fell upon an inside ring adjustable to the day and month. It required careful orienting to be dependable as a time-indicator.

Sun-Dials, Roman—The first dial in Rome was set up B. C. 293 near the temple of Quirinus by Papirius Cursor. It served ninety-nine years; then one more accurate was set up beside it. Before that, no time was noted except the rising and setting of the sun. Emperor Augustus erected a dial at Campus Martius. A dial captured in Sicily during the first Punic war was set up in the Forum about 263 B. C. and used for years before they learned that it was inaccurate in that latitude, being designed for the latitude of Sicily.

Sunk-Seconds—A dial in which the seconds circle is sunk below the rest of the dial. It allows the hour hand to be placed closer to the face thus making a thinner model possible.

Supplementary Arc—See: "Lifting Arc."

Sweep-Seconds—See: Center-Seconds.

Table Roller—The roller of a lever escapement which carries the impulse pin.

Tell-Tale Clock—A clock by which a record is left of periodical visits of some one as a night-watchman.

Template or Timplet—One of the four facets that surround a cut gem.

Tenon—A projection at the end of a piece cut to fit into a corresponding mortise.

Terry, Eli—The first man to make clocks by machinery in America. When it was learned that he planned to make two hundred clocks he was much laughed at. He was born at East Windsor, Conn., in 1772. His first clocks were made by hand, the movements being of wood. He was the leading maker of wooden clocks in America. He invented the shelf clock which contained distinctly new inventions and he introduced the pillar scroll-top case. He was a mechanical genius and contributed a great deal to developing clock-making in America into a great industry. He died in 1852.

Third Wheel—The wheel in the train between the center wheel and the fourth wheel.

Thales—A celebrated Ionian astronomer, one of the Seven Sages of Greece. He was born about 640 B. C., and is credited by Herodotus with having predicted an eclipse of the sun occurring about 609 B. C. He was the author of several solutions of geometrical problems. He died about 550 B. C.

Thomas, Seth—Born at Wolcott, Conn., 1785. A very successful clockmaker who contributed probably more than any other man toward popularizing the modern cheap clock. The Seth Thomas Clock Co., of today, he started in 1813 with twenty operatives. By 1853 it had nine hundred. He died in 1859.

Three-Quarter Plate—A three-quarter plate watch is one in which there is a piece cut out from the top plate large enough to permit the balance to rotate on a level with that plate. It is the most common form at present in use in both cheap and high grade watches, and found in both "pillar" and "bridge" models.

Time-Candles—Candles in alternate black and white sections were used to mark the passage of time in Europe and Asia for a long time. In England and France they were used to limit the bidding at an auction. The phrase "by inch of candle" meant that the one bidding when the flame expired was the successful bidder. King Alfred is said to have used time-candles and to have inclosed them in thin horn plates to protect them from drafts, thus originating the lantern.

Timekeeper—Any device primarily concerned with measuring and indicating the sub-divisions of the day.

Tompion, Thomas—"The father of English Watchmaking." Born 1638. He was the leading watchmaker at the court of Charles II. He found the construction of the time-keeping part of watches in a very indifferent condition and he left English clocks and watches the finest in the world, although many great improvements were made after his time. He associated closely with such scientists as Hooke, and Barlow, and made practical application of their theories—two notable instances being the cylinder escapement and the balance-spring. Tompion was the first to number his watches consecutively for the purpose of identification though he did not so mark his early ones. There is a famous clock in the pumproom at Bath, England, of Tompion's construction. Little is known of his domestic life but he appears to have been unmarried. He died in 1713 and is buried in Westminster Abbey. Tompion was master of the Worshipful Clockmakers' Company in 1704.

Top Plate—The plate in a watch farthest from the dial. In full plate watches it is circular; in three-quarter plate or half-plate watches a part is cut away.

Tower of the Winds—An octagonal tower north of the Acropolis of Athens spoken of as horological by Vario and Vitruvius. Believed to have had a sundial on each of its eight faces and to have contained a clepsydra fed by a spring.

Train—The toothed wheels of a watch or clock which connect the barrel or fusee with the escapement. In a going-barrel watch the teeth about the barrel drive the center pinion which drives the center wheel and then in turn the third wheel pinion, third wheel, fourth wheel pinion and fourth wheel, escape pinion and escape wheel.

Tripping—The running past the pallet's locking face, of an escape wheel tooth.

Vacheron and Constantin—In 1840 established the first complete watch factory in Switzerland. Not until later, however, was motor power used instead of foot-power; and later still manufacture by machinery. The work in this factory is carried on under a combination of all accepted methods.

Vailly, Dom—A Benedictine monk of about 1690 who made a water clock which Beckmann says was the first to be constructed on a really scientific principle. See Clocks, Interesting Old—Vailly's.

Van der Woerd, Charles—A prominent man in connection with watch manufacturing in this country. In 1864 he invented an automatic pinion cutter; in 1874 an automatic screw machine. From 1876-1883 he was superintendent of the Waltham factory.

Verge—The pallet axis of the verge escapement. See diagram of Verge Escapement. It carries the balance at its top.

Verge Watch—A watch with a verge escapement.

Vick, Henry de. See De Vick.

Volute—A flat spiral.

Volute-Spring—A flat metallic spring coiled in a spiral conical form and compressible in the direction of its axis.

Wallingford, Richard—An English mechanic and astronomer of the fourteenth century. He made a clock which is supposed to have been the first that was regulated by a fly-wheel. Several authorities, however, claim that Wallingford's "clock" was actually a planetarium.

Waltham—A town in Massachusetts—the site of the first successful watch factory in America. At present a great watch making center.

Watch—In modern parlance, a small timepiece to carry about on the person. Formerly a timepiece which showed time in distinction to clock which struck time. Derham (1734) uses the term to indicate all timepieces driven by springs. The term may have been derived from the Swedish vacht, German wachen, or Saxon woecca. The spaces of time between the fillings of a clepsydra were also called "watches."

Watch Collections—For list of principal collections, past and present, see Jewelers' Circular files August to December 1915. List compiled by Major Paul M. Chamberlain of Chicago. For list of principal present collections, see Appendix to this volume derived from the Chamberlain Compilation.

Watchmakers' Schools—American. In America these schools usually teach watch-repairing and not the making of watches. Some of them offer courses in making watches but few pupils avail themselves of these courses. List of: De Selins Watch School, Attica, Ind.; Detroit Technical Institute—Detroit, Mich.; Kansas City Watchmaking and Engraving School, Kansas City, Mo.; Needles Institute of Watchmaking, Kansas City, Mo.; Bowman Technical School, Lancaster, Pa.; Ries and Armstrong, Macon, Ga.; Drexler School for Watchmaking, Milwaukee, Wis.; Newark Watchmaking School, Newark, N. J.; Philadelphia College of Horology, Philadelphia, Pa.; St. Louis Watchmaking School, St. Louis, Mo.; Schwartzman's Trade Schools, San Francisco, Cal.; Stone School of Watchmaking, St. Paul, Minn.; Waltham Horological School, Waltham, Mass.; Bradley Polytechnic Institute, Peoria, Ill.

Watchmakers' Schools, Switzerland—Usually under government management. Teach very thoroughly and completely the art of making a watch from the beginning.

Watch-Papers—During the 18th century it was a fad in England and America to carry small round papers, which exactly fitted the case of a watch. On these were portraits and verses, the latter of doubtful merit and usually of sinister or gloomy significance.

Waterbury—A town in Connecticut long a center of clock and watch making in America. Home of the original Waterbury watch. Location of principal factory of Robt. H. Ingersoll & Brothers., manufacturers of the Ingersoll watches.

Water-Clock—Any device, as a clepsydra, for measuring time by the fall or flow of water. More commonly applied to the type in which wheels are turned by water or in such as those in which water sets machinery of some form in motion as Vailly's water-clock. See Clock, Vailly's.

Wick Timekeeper—A wick or rope made of some fiber resembling flax or hemp with knots tied at regular intervals and so treated that upon ignition it would smolder instead of breaking into flame. Early in use in Japan and China. Time was estimated by the burning between the knots.

Wieck, Henry De—See De Vick.

Willard, Aaron—Born 1757. Probably learned his trade from his older brothers Simon and Benjamin. He made tall, and shelf clocks, later banjo clocks—so-called from their shape—gallery clocks, and regulators. A better business man than his brothers and successful from the start. His clocks did not lack decorative merit but were inferior to Simon Willard's. He made a greater number than his brother because more successful in a business way.

Willard, Benjamin—Older brother of Simon and Aaron Willard. Among the first of American clockmakers. Born 1743. Made, probably, only tall clocks with handsome cases and some with musical attachments. Not so good as the clocks of Aaron and Simon Willard but older and rarer now.

Willard, Simon—Born at Grafton, Mass., 1753. One of the earliest Massachusetts clock makers who disputed the claim of the Connecticut makers for the credit of revolutionizing the clock industry in America. So far as cases go they excelled Terry, Thomas, and others. But to the Connecticut makers belongs the credit for having developed clock making into a great industry. Willard at first made eight-day tall clocks and shelf clocks, later wall clocks which he called "time pieces." In 1802 he practically abandoned the making of tall clocks, and confined himself to his "time pieces" and special orders for tower and gallery clocks. For a detailed list of his productions see his Biography by John Ware Willard. He was an intimate friend of Jefferson, Madison and other leading men of the time. Died 1848.

Worshipful Clockmakers' Company of London, The—Incorporated August 22, 1631, under special charter by King Charles I of England. Was given the sole privilege of regulating the watch and clock trade in and for ten miles around London.

Webster, Ambrose—Mechanical superintendent, and later assistant superintendent, of the Waltham factory until his resignation in 1876. He systematized the work in the shop, standardized the measuring system, and forced automatic machinery to the front. He designed the first watch factory lathe with hard spindles and bearings of the two taper variety. He made the first interchangeable standard for parts of lathes. He invented many machines now in use, among them being the automatic pinion cutter.

Weight-Clock—A clock whose driving power is a weight suspended by a cord wound on a drum or cylinder.

Weights—The first clocks were made with a weight on a cord which was wound around a cylinder connected with the train. The weight descending caused the cylinder to revolve, setting the train in motion. Too rapid unwinding was prevented by the escapement. The weight as a driving power is still used, especially in large clocks.

Wheel, Count—The wheel carrying the locking-plate in a striking mechanism.

Year—Astronomically, the period of time occupied by the earth in making one complete revolution around the sun. The calendar year is an arbitrarily determined division of time, approximating more or less closely the astronomical year. See Calendar, Gregorian.

Zech, Jacob—Of Prague. Invented the fusee about 1525. The Society of Antiquaries possesses an example of his handiwork—a table time-piece with a circular brass-gilt case 9¾" in diameter and 5" high. For minute description see Archaeologia vol. xxxiii.

Zero—A time-telling term originating or at least made common during the Great War. Word commonly used in a military sense to indicate a secret instant of time from which an attack in its various stages is scheduled.

Zodiac—An imaginary belt 16 degrees in width, spread equally on both sides of the ecliptic (q. v.). It is divided into twelve sections or "signs" which receive their distinguishing names from the twelve principal constellations within the belt. That is how the Babylonians learned to tell the time by looking at the sun and the stars. Only their whole problem was vastly complicated by the daily rotation of the earth on its axis, which of course makes the whole sky seem to turn in the opposite direction day by day. The earth turns in the same direction that it goes round the sun, from West to East. So the heavens turn apparently from East to West, while the annual motion, as we saw just now by the illustration of the clock face, appears in its true direction, Eastward. Also, the great clock of the sky is not from our point of view horizontal, but stood up on edge; and not straight up and down even, but slanted at an angle. So its apparent movements are as it were in several directions at once, and the effect is very confusing. The real motions as they actually do occur are very much simpler and easier to understand. But of these the Babylonians had no idea. They knew only what they could see; and it is all the more wonderful that they contrived to reason out so much and so correctly.

They mapped out a belt or zone around the sky, with the Ecliptic along the middle of it. This they divided into twelve equal parts of thirty degrees each, called Signs or Houses, and each containing a constellation. These constellations were in order, Aries or the Ram; Taurus or the Bull; Gemini or the Twins; Cancer or the Crab; Leo or the Lion; Virgo or the Virgin; Libra or the Scales; Scorpio or the Scorpion; Sagittarius or the Archer; Capricornus or the Goat; Aquarius or the Water-Carrier; and Pisces or the Fishes. We know these by their Latin names, and the whole zone by its Greek name of The Zodiac. But their original titles were much the same, only in a different language. The sun went through one of these constellations each month; and by his position along the Zodiac they told the time of year. Thus the Spring Equinox was where the sun entered the House of the Ram; and that was for the ancients the first day of the new year. The House of the Crab was farthest North, and when the sun got there it was midsummer. The Autumn Equinox was in the House of the Scales; and when the sun reached the House of the Goat, he would be at the Southern or Winter end of his journey. Moreover, since the Moon and the Planets always keep close to the Ecliptic, their apparent motions all lie within the Zodiacal zone. And the Zodiac therefore represented the most important part of the heavens from the standpoint of keeping time; the part, that is, wherein all of those bodies which moved among the stars month by month and day by day appeared to have their motions.