John Platts

CURIOSITIES RESPECTING THE ARTS.—(Concluded.)

Burning Glasses—Ductility of Glass—Remarkable Ductility and Extensibility of Gold—Pin Making—Needles—Shoes—The Great Bell of Moscow.

Burning Glasses.—We have some extraordinary instances and surprising accounts of prodigious effects of burning-glasses. Those made of reflecting mirrors are more powerful than those made with lenses, because the rays from a mirror are reflected all to one point nearly; whereas by a lens, they are refracted to different points, and are therefore not so dense or ardent. The whiter also the metal or substance is, of which the mirror is made, the stronger will be the effect.

The most remarkable burning-glasses, or rather mirrors, among the ancients, were those of Archimedes and Proclus; by the first of which the Roman ships, besieging Syracuse, (according to the testimony of several writers,) and by the other, the navy of Vitalian besieging Byzantium, were reduced to ashes. Among the moderns, the burning mirrors of greatest eminence, are those of Vilette, and Tschirnhausen, and the new complex one of M. de Buffon.

That of M. de Vilette was three feet eleven inches in diameter, and its focal distance was three feet two inches. Its substance is a composition of tin, copper, and tin glass. Some of its effects, as found by Dr. Harris and Dr. Desaguliers, are, that a silver sixpence melted in seven seconds and a half; a king George’s halfpenny melted in sixteen seconds, and ran in thirty-four seconds; tin melted in three seconds; and a diamond weighing four grains, lost seven-eighths of its weight. That of M. de Buffon is a polyhedron, six feet broad, and as many high, consisting of one hundred and sixty-eight small mirrors, or flat pieces of looking-glass, each six inches square; by means of which, with the faint rays of the sun in the month of March, he set on fire boards of beechwood at one hundred and fifty feet distance. Besides, his machine has the conveniency of burning downwards, or horizontally, at pleasure; each speculum being moveable, so as, by the means of three screws, to be set to a proper inclination for directing the rays towards any given point; and it turns either in its greater focus, or in any nearer interval, which our common burning-glasses cannot do, their focus being fixed and determined. M. de Buffon, at another time, burnt wood at the distance of two hundred feet. He also melted tin and lead at the distance of above one hundred and twenty feet, and silver at fifty.

Mr. Parker, of Fleet-street, London, was induced, at an expense of upwards of £700, to contrive, and at length to complete, a large transparent lens, that would serve the purpose of fusing and vitrifying such substances as resist the fires of ordinary furnaces, and more especially of applying heat in vacuo, and in other circumstances in which it cannot be applied by any other means. After directing his attention for several years to this object, and performing a great variety of experiments in the prosecution of it, he at last succeeded in the construction of a lens, of flint-glass, three feet in diameter, which, when fixed in its frame, exposes a surface two feet eight inches and a half in the clear, without any other material imperfection, except a disfigurement of one of the edges by a piece of the scoria of the mould, which unfortunately found its way into its substance. This lens was double-convex, both sides of which were a portion of a sphere of eighteen feet radius. It is difficult to form an accurate estimate of the burning power of this lens; inasmuch as it is next to impossible to discover what should be deducted for the loss of power, in consequence of the impediments that the glass of which it was made must occasion, as well as the four reflections, and two more by way of diminution; but we will endeavour to appreciate it, after a full allowance for these deductions, which must necessarily result from every means of concentrating the solar rays, and must be considered as the friction of an engine, of which nature they really partake.

The solar rays received on a circular surface of two feet eight inches and a half, when concentrated within the diameter of an inch, will be 105,626 times its intensity, or this number of times greater than the heat of the sun as it is experienced on the surface of the earth. We will suppose, that as the heat of the air, in ordinary summer weather, is 65 degrees, and in sultry weather is 75 degrees, the average of which is 70 degrees, and that we take this as the average effect, the accumulated power of the lens, on the supposition of an uniform heat over the whole surface of the focus, will be equal to 73,938 degrees. It must be recollected, by those who have an opportunity of examining the effects of this lens, that the external part of the focal light was less intense than that part which was near the centre of it; or rather, that the effect was very much accumulated in the centre; but as it is possible that the refraction of the light and of the caloric fluid may not take place in the same angles, we think it safest to consider it as of uniform effect, and alter deducting one fourth part thereof as a compensation, there remains 5545 as the expression of its power. As the application of the second lens reduced the diameter of the focus to half an inch, the effect, without allowing for the reduction of its power, would be equal to 221,816 degrees; but deducting one-fourth for the second transmission, there remains 166,362 degrees, as the expression of its power.

Mr. Parker further informs us, that a diamond, weighing ten grains, exposed to this lens for thirty minutes, was reduced to six grains; during which operation it opened and foliated like the leaves of a flower, which emitted whitish fumes, and when closed again, bore a polish, and retained its form. Gold remained in its metallic state without apparent diminution, notwithstanding an exposure at intervals of many hours: but what is remarkable, the rest, or cupel, which was composed of bone-ash, was tinctured with a beautiful pink colour.

The experiments on platina evince that the specimens were in different states of approach to a complete metallic form; several of them threw off their parts in sparks, which in most instances were metallic. Copper, after three minutes’ exposure, was not found to have lost in weight.

What is remarkable with regard to experiments on iron, is, that the lower part, i. e. that part in contact with the charcoal, was first melted, when that part which was exposed to the focus remained unfused; an evidence of the effect of flux on this metal.

Several of the semi-crystalline substances, exposed to the focal heat, exhibited symptoms of fusion; such as the agate, oriental flint, cornelian, and jasper: but as the probability is, that these substances were not capable of complete vitrification, it is enough that they were rendered externally of a glassy form. Garnet completely fused on black lead in 120 seconds, lost a quarter of a grain, became darker in colour, and was attracted by the magnet. Ten cut garnets taken from a bracelet began to run the one into the other in a few seconds, and at last formed into one globular garnet. The clay used by Mr. Wedgwood to make his pyrometric test, run in a few seconds into a white enamel. Seven other kinds of clay, sent by Mr. Wedgwood, were all vitrified. Several experiments were made on limestone, some of which were vitrified, but all of which were agglutinated; it is, however, suspected that some extraneous substance must have been intermixed. A globule produced from one of the specimens, on being put into the mouth, flew into a thousand pieces, occasioned, it is presumed, by the moisture.

A subscription was proposed for raising the sum of seven hundred guineas, towards indemnifying the charges of the inventor, and retaining the very curious and useful machine above described in our own country; but from the failure or the subscription, and some other concurring circumstances, Mr. Parker was induced to dispose of it to Capt. Mackintosh, who accompanied Lord Macartney in the embassy to China: and it was left, much to the regret of philosophers in Europe, at Pekin; where it remains in the hands of persons, who most probably know neither its value nor use.

Ductility of Glass.—We all know, that when glass is well penetrated with the heat of the fire, the workmen can figure and manage it like soft wax; but, what is most remarkable, it may be drawn, or spun out, into threads exceedingly long and fine. Our ordinary spinners do not form their threads of silk, flax, or the like, with half the ease and expedition the glass-spinners do threads of this brittle matter. We have some of them used in plumes for children’s heads, and divers other works, much finer than any hair, and which bend and wave, like hair, with every wind. Nothing is more simple and easy than the method of making them. There are two workmen employed: the first holds one end of a piece of glass over the flame of a lamp; and when the heat has softened it, a second operator applies a glass hook to the metal thus in fusion, and, withdrawing the hook again, it brings with it a thread of glass, which still adheres to the mass; then, fitting his hook on the circumference of a wheel about two feet and a half in diameter, he turns the wheel as fast as he pleases, which, drawing out the thread, winds it on its run, till, after a certain number of revolutions, it is covered with a skein of glass-thread. The mass in fusion over the lamp diminishes insensibly, being wound out like a clue of silk upon the wheel; and the parts cooling as they recede from the flame, become more coherent to those next to them, and this by many degrees: the parts nearest the fire are always the least coherent, and, of consequence, must give way to the effort the rest make to draw them towards the wheel. The circumference of these threads is usually a flat oval, being three or four times as broad as thick: some of them seem scarcely bigger than the thread of a silkworm, and are surprisingly flexible. If the two ends of such threads are knotted together, they may be drawn and bent, till the aperture, or space in the middle of the knot, does not exceed one-fourth of a line, or one forty-eighth of an inch in diameter. Hence M. Reaumur maintains, that the flexibility of glass increases in proportion to the fineness of the threads; and that, probably, had we but the art of drawing threads as fine as a spider’s web, we might weave stuffs and cloths of them for wear. Accordingly, he made some experiments this way; and found that he could make threads fine enough, viz. as fine, in his judgment, as spider’s thread, but not long enough for the purposes of any manufacture.

Remarkable Ductility and Extensibility of Gold.—Gold is the most ductile, as well as the most malleable, of all metals. According to Cronstedt, one grain of it may be stretched out so as to cover 98 Swedish ells, equal to 63.66 English yards of silver wire; but Wallerius asserts, that a grain may be stretched out in such a manner, as to cover 500 ells of wire. At any rate, the extension is prodigious; for, according to the least of the calculations, the millionth part of a grain of gold may be made visible to the naked eye. Nor is its malleability inferior to its ductility. Boyle, quoted by Apligny, in his treatise on Colours, says, that one grain and a half of gold may be beaten into 50 leaves of an inch square, which, if intersected by parallel lines drawn at right angles to each other, and distant only the hundredth part of an inch from each other, will produce twenty-five millions of little squares, each very easily discernible by the naked eye. Mr. Magellan tells us, that its surface may be extended by the hammer 159,092 times. “I am informed, (says he) by an intelligent goldbeater in England, that the finest gold leaf is that made in new skins, and must have an alloy of three grains of copper to the ounce of pure gold, or else it would be too soft to pass over the irregularities of the skins. He affirms, that 80 books, or 2000 leaves of gold, each leaf containing 10.89 square inches, weigh less than 384 grains. Each book, therefore, of 25 leaves, or 272.25 inches, weighs less than 4.8 grains; so that each grain of the metal will produce about 57 square inches of gold leaf.” From further calculation it appears, that the thickness of these leaves is less than the 282,000th part of an inch; and that 16 ounces of gold would be sufficient to gild a silver wire, equal in length to the whole circumference of the globe we inhabit!

Pin-making.—Though pins are apparently simple, their manufacture is not a little curious and complex. When the brass wire, of which the pins are formed, is first received at the manufactory, it is generally too thick for the purpose of being cut into pins. The first operation, therefore, is that of winding it off from one wheel to another with great velocity, and causing it to pass between the two, through a circle in a piece of iron of smaller diameter. The wire being thus reduced to its proper dimensions, is straightened by drawing it between iron pins, fixed in a board in a zigzag manner, but so as to leave a straight line between them: afterwards it is cut into lengths of three or four yards, and then into smaller ones, every length being sufficient to make six pins. Each end of these is ground to a point, which was performed, (where these observations were made,) by boys, who sat each with two small grinding-stones before him, turned by a wheel. Taking up a handful, he applied the ends to the coarsest of the two stones, being careful at the same time to keep each piece moving round between his fingers, so that the points may not become flat: he then gives them a smoother and sharper point by applying them to the other stone, and by that means a lad of twelve or fourteen years of age, is able to point about sixteen thousand pins in an hour. When the wire is thus pointed, a pin is taken off at each end, and this is repeated till it is cut into six pieces. The next operation is, that of forming the heads, or, as they term it, head-spinning, which is done by means of a spinning-wheel, one piece of wire being thus with astonishing rapidity wound round another, and the interior one being drawn out, leaves a hollow tube between the circumvolutions: it is then cut with shears, every two circumvolutions, or turns of the wire, forming one head; these are softened by throwing them into iron pans, and placing them in a furnace till they are red hot. As soon as they are cold, they are distributed to children, who sit with hammers and anvils before them, and catching one at the extremity, they apply them immediately to the anvil and hammer, and by a motion or two of the foot, the top and the head are fixed together in much less time than it can be described, and with a dexterity only to be acquired by practice. The pin is now finished as to its form, but still it is merely brass; it is therefore thrown into a copper containing a solution of tin and the lees of wine. Here it remains for some time, and, when taken out, assumes a white, though dull appearance: in order therefore to give it a polish, it is put into a tub containing a quantity of bran, which is set in motion by turning a shaft that runs through its centre, and thus, by means of friction, it becomes perfectly bright. The pin being complete, nothing remains but to separate it from the bran, which is perfectly similar to the winnowing of corn, the bran flying off, and leaving the pin behind it for immediate sale.

We must not forget to present to the reader some curious particulars respecting the manufacture of Needles.—Needles make a very considerable article in commerce, though there is scarcely any commodity cheaper, the consumption of them being almost incredible. The sizes are from No. 1, the largest, to No. 25, the smallest. In the manufacture of needles, German and Hungarian steel are of most repute.

In the making of them, the first thing is, to pass the steel through a coal fire, and under a hammer, to bring it out of its square figure into a cylindrical one. This done, it is drawn through a large hole of a wire-drawing iron, and returned into the fire, and drawn through a second hole of the iron, smaller than the first; and thus successively from hole to hole, till it has acquired the degree of fineness required for that species of needles; observing, every time it is to be drawn, that it be greased over with lard, to render it more manageable. The steel, thus reduced to a fine wire, is cut in pieces of the length of the needles intended. These pieces are flatted at one end on the anvil, by force of a puncheon of well-tempered steel, and laid on a leaden block to bring out, with another puncheon, the little piece of steel remaining in the eye. The corners are then filed off the square of the heads, and a little cavity filed on each side of the flat of the head; this done, the point is formed with a file, and the whole filed over: they are then laid to heat red-hot on a long narrow iron, crooked at one end, in a charcoal fire; and when taken out thence, are thrown into a bason of cold water to harden. On this operation a good deal depends; too much heat burns them, and too little leaves them soft; the medium is learned by experience. When they are thus hardened, they are laid in an iron shovel on a fire more or less brisk in proportion to the thickness of the needles; taking care to move them from time to time. This serves to temper them, and take off their brittleness; great care here too must be taken of the degree of heat. They are then straightened one after another with the hammer, the coldness of the water used in hardening them having twisted the greatest part of them.

The next process is the polishing of them. To do this, they take 12,000 or 15,000 needles, and range them in little heaps against each other, on a piece of new buckram sprinkled with emery-dust. The needles being thus disposed, emery-dust is thrown over them, which is again sprinkled with oil of olives; at last the whole is made up into a roll, well bound at both ends. This roll is then laid on a polishing table, and over it a thick plank loaded with stones, which two men work backwards and forwards a day and a half, or two days, successively; by which means the roll thus continually agitated by the weight and motion of the plank over it, the needles withinside being rubbed against each other with oil and emery, are insensibly polished. After polishing, they are taken out, and the filth washed off them with hot water and soap: they are then wiped in hot bran, a little moistened, placed with the needles in a round box suspended in the air by a cord, which is kept stirring till the bran and needles are dry. The needles thus wiped in two or three different brans, are taken out and put in wooden vessels, to have the good separated from those whose points or eyes have been broken either in polishing or wiping; the points are then all turned the same way, and smoothed with an emery-stone turned with a wheel. This operation finishes them, and there remains nothing but to make them into packets.Needles were first made in England by a native of India, in 1545, but the art was lost at his death; it was, however, recovered by Christopher Greening, in 1560, who was settled, with his three children, Elizabeth, John, and Thomas, by Dr. Damar, ancestor of the present Lord Milton, at Long Crendon, in Bucks, where the manufactory has been carried on from that time to the present day.

Curiosities respecting Shoes.—Among the Jews, shoes were made of leather, linen, rush, or wood; those of soldiers were sometimes of brass or iron. They were tied with thongs, which passed under the soles of the feet. To put off their shoes, was an act of veneration; it was also a sign of mourning and humiliation: to bear one’s shoes, or to untie the latchets of them, was considered as the meanest service, as appears in the Baptist’s declaration of his own inferiority to Christ.

Among the Greeks, shoes of various kinds were used. Sandals were worn by women of distinction. The Lacedemonians wore red shoes. The Grecian shoes generally reached to the middle of the leg. The Romans used two kinds of shoes: the calceus, which covered the whole foot, somewhat like our shoes, and was tied above with latchets or strings; and the solea, or slipper, which covered only the sole of the foot, and was fastened with leathern thongs. The calceus was always worn along with the toga, when a person went abroad: slippers were put on during a journey, and at feasts, but it was reckoned effeminate to appear in public with them. Black shoes were worn by the citizens of ordinary rank, and white ones by the women. Red shoes were sometimes worn by the ladies, and purple ones by the coxcombs of the other sex. Red shoes were put on by the chief magistrates of Rome, on days of ceremony and triumphs. The shoes of senators, patricians, and their children, had a crescent upon them, which served for a buckle; these were called calcei lunati. Slaves wore no shoes; hence they were called cretori, from their dusty feet. Phocion also, and Cato Uticensis, went without shoes. The toes of the Roman shoes were turned up in the point; hence they were called calcei rostrati, repandi, &c.

In the ninth and tenth centuries, the greatest princes of Europe wore wooden shoes, or the upper part of leather, and the sole of wood. In the reign of William Rufus, a great beau, Robert, surnamed The Horned, used shoes with long sharp points, stuffed with tow, and twisted like a ram’s horn. It is said, the clergy being highly offended, declaimed against the long-pointed shoes with great vehemence. The points, however, continued to increase, till, in the reign of Richard II. they were of so enormous a length, that they were tied to knees with chains, sometimes of gold, sometimes of silver. The upper parts of these shoes, in Chaucer’s time, were cut in imitation of a church window. The long-pointed shoes were called crackowes, and continued in fashion for three centuries, in spite of the bulls of popes, the decrees of councils, and the declamations of the clergy. At length the parliament of England interposed, by an act A. D. 1463, prohibiting the use of shoes or boots with pikes exceeding two inches in length, and prohibiting all shoemakers from making shoes or boots with longer pikes, under severe penalties. But even this was not sufficient: it was necessary to denounce the dreadful sentence of excommunication against all who wore shoes or boots with points longer than two inches. The present fashion of shoes was introduced in 1633, but the buckle was not used till 1670.

In Norway, they use shoes of a particular construction, consisting of two pieces, and without heels; in which the upper-leather sits close to the foot, the sole being joined to it by many plates or folds.

The shoes or slippers of the Japanese, as we are informed by Professor Thunberg, are made of rice-straw, woven; but sometimes, for people of distinction, of fine slips of ratan. The shoe consists of a sole, without upper-leather or hind-piece: forwards, it is crossed by a strap, of the thickness of one’s finger, which is lined with linen; from the tip of the shoe to the strap, a cylindrical string is carried, which passes between the great and second toe, and keeps the shoe fast on the foot. As these shoes have no hind-piece, they make a noise, when people walk in them, like slippers. When the Japanese travel, their shoes are furnished with three strings made of twisted straw, with which they are tied to the legs and feet, to prevent them from falling. Some people carry one or more pairs of shoes with them on their journeys, in order to put on new when the old ones are worn out. When it rains, or the roads are very dirty, these shoes are soon wetted through; and a great number of worn-out shoes are continually seen lying on the roads, especially near the brooks, where travellers have changed their shoes after washing their feet.

Instead of these, in rainy or dirty weather, they wear high wooden clogs, which underneath are hollowed out in the middle, and at top have a band across, like a stirrup, and a string for the great toe; so that they can walk without soiling their feet. Some of them have their straw shoes fastened to these wooden clogs. The Japanese never enter their houses with their shoes on; but leave them in the entry, or place them on the bench near the door, and thus are always barefooted in their houses, so as not to dirty their neat mats.

Great Bell of Moscow. From Dr. Clarke’s Travels.—“The great bell of Moscow, known to be the largest ever founded, is in a deep pit in the midst of the Kremlin. The history of its fall is a fable; and as writers are accustomed to copy each other, the story continues to be propagated. The fact is, the bell remains in the place where it was originally cast. It never was suspended; the Russians might as well attempt to suspend a first-rate line-of-battle ship, with all her guns and stores. A fire took place in the Kremlin; the flames caught the building erected over the pit where the bell yet remains; in consequence of this, the bell became hot, and water being thrown to extinguish the fire, fell upon the bell, causing the fracture which has taken place. The bell reaches from the bottom of the cave to the roof. The entrance is by a trap-door, placed even with the surface of the earth. We found the steps very dangerous; some were wanting, and others broken. In consequence of this, I had a severe fall down the whole extent of the first flight, and a narrow escape for my life, in not having my skull fractured upon the bell. After this accident, a sentinel was placed at the trap-door, to prevent people becoming victims to their curiosity. He might have been as well employed in mending the ladders, as in waiting all day to say they were broken. The bell is truly a mountain of metal. It is said to contain a very large proportion of gold and silver. While it was in fusion, the nobles and the people cast in, as votive offerings, their plate and money: I endeavoured in vain to assay a small part: the natives regard it with superstitious veneration, and they would not allow even a grain to be filed off. At the same time, it may be said, the compound has a white shining appearance, unlike bell-metal in general; and, perhaps, its silvery aspect has strengthened, if not excited, a conjecture respecting the costliness of its constituents.

“On festival days, peasants visit the bell as they would resort to a church; considering it an act of devotion, and crossing themselves as they descend and ascend the steps. The bottom of the pit is covered with water, mud, and large pieces of timber; these, added to the darkness, render it always an unpleasant and unwholesome place; in addition to the danger arising from the ladders leading to the bottom. I went frequently there, in order to ascertain the dimensions of the bell with exactness. To my great surprise, during one of those visits, half a dozen Russian officers, whom I found in the pit, agreed to assist me in the admeasurement. It so nearly agreed with the account published by Jonas Hanway, that the difference is not worth notice. This is somewhat remarkable, considering the difficulty of exactly measuring what is partly buried in the earth, and the circumference of which is not entire. No one, I believe, has yet ascertained the size of the base; this would afford still greater dimensions than those we obtained; but it is entirely buried. About ten persons were present when I measured the part exposed to observation. We applied a strong cord close to the metal, in all parts of its periphery, and round the lower part, where it touches the ground, taking care at the same time not to stretch the cord. From the piece of the bell broken off, it was ascertained that we had thus measured within two feet of its lower extremity. The circumference obtained was sixty-seven feet four inches; allowing a diameter of twenty-two feet five inches, and one-third. We then took the perpendicular height from the top, and found it to correspond exactly with the statement made by Hanway; namely, twenty-one feet four inches and a half. In the stoutest part, that in which it should have received the blow of the hammer, its thickness equalled twenty-three inches. We were able to ascertain this, by placing our hands under water, where the fracture has taken place; this is above seven feet high from the lip of the bell. The weight of this enormous mass of metal has been computed to be 443,772 cwt. which, if valued at three shillings a pound, amounts to £66,565 16s. lying unemployed, and of no use to any one.”

It was founded, according to Augustine, in 1653, during the reign of Alexis. (See Voyage de Moscow, page 117.) The Russians and people of Moscow maintain, that it was cast during the reign of their empress Anne, probably from the female figure represented. Augustine proves that it is larger than the famous bell of Erford, and even than that of Pekin.