1 From a photograph, with figures, to show the relative size of the tube aperture.

2 Weld’s History of the Royal Society, vol. ii. p. 188.

3 Dr. Whewell (Bridgewater Treatise, p. 266) well observes, that Boyle and Pascal are to hydrostatics what Galileo is to mechanics, and Copernicus, Kepler, and Newton are to astronomy.

4 The Rev. Mr. Turnor recollects that Mr. Jones, the tutor, mentioned, in one of his lectures on optics, that the reflecting telescope belonging to Newton was then lodged in the observatory over the gateway; and Mr. Turnor thinks that he once saw it, with a finder affixed to it.

5 The story of the dog “Diamond” having caused the burning of certain papers is laid in London, and in Newton’s later years. In the notes to Maude’s Wenleysdale, a person then living (1780) relates, that Sir Isaac being called out of his study to a contiguous room, a little dog, called Diamond, the constant but incurious attendant of his master’s researches, happened to be left among the papers, and by a fatality not to be retrieved, as it was in the latter part of Sir Isaac’s days, threw down a lighted candle, which consumed the almost finished labour of some years. Sir Isaac returning too late but to behold the dreadful wreck, rebuked the author of it with an exclamation (ad sidera palmas), “O Diamond! Diamond! thou little knowest the mischief done!” without adding a single stripe. M. Biot gives this fiction as a true story, which happened some years after the publication of the Principia; and he characterises the accident as having deprived the sciences forever of the fruit of so much of Newton’s labours.—Brewster’s Life, vol. ii. p. 139, note. Dr. Newton remarks, that Sir Isaac never had any communion with dogs or cats; and Sir David Brewster adds, that the view which M. Biot has taken of the idle story of the dog Diamond, charged with fire-raising among Newton’s manuscripts, and of the influence of this accident upon the mind of their author, is utterly incomprehensible. The fiction, however, was turned to account in giving colour to M. Biot’s misrepresentation.

6 Bohn’s edition.

7 When at Pisa, many years since, Captain Basil Hall investigated the origin and divergence of the tower from the perpendicular, and established completely to his own satisfaction that it had been built from top to bottom originally just as it now stands. His reasons for thinking so were, that the line of the tower, on that side towards which it leans, has not the same curvature as the line on the opposite, or what may be called the upper side. If the tower had been built upright, and then been made to incline over, the line of the wall on that side towards which the inclination was given would be more or less concave in that direction, owing to the nodding or “swagging over” of the top, by the simple action of gravity acting on a very tall mass of masonry, which is more or less elastic when placed in a sloping position. But the contrary is the fact; for the line of wall on the side towards which the tower leans is decidedly more convex than the opposite side. Captain Hall had therefore no doubt whatever that the architect, in rearing his successive courses of stones, gained or stole a little at each layer, so as to render his work less and less overhanging as he went up; and thus, without betraying what he was about, really gained stability.—See Patchwork.

8 Lord Bacon proposed that, in order to determine whether the gravity of the earth arises from the gravity of its parts, a clock-pendulum should be swung in a mine, as was recently done at Harton colliery by the Astronomer-Royal.

When, in 1812, AmpÈre noted the phenomena of the pendulum, and showed that its movement was produced only when the eye of the observer was fixed on the instrument, and endeavoured to prove thereby that the motion was due to a play of the muscles, some members of the French Academy objected to the consideration of a subject connected to such an extent with superstition.

9 This curious fact was first recorded by Pepys, in his Diary, under the date 31st of July 1665.

10 The result of these experiments for ascertaining the variation of the gravity at great depths, has proved beyond doubt that the attraction of gravitation is increased at the depth of 1250 feet by 1/19000 part.

11 See the account of Mr. Baily’s researches (with two illustrations) in Things not generally Known, p. vii., and “Weight of the Earth,” p. 16.

12 Fizeau gives his result in leagues, reckoning twenty-five to the equatorial degree. He estimates the velocity of light at 70,000 such leagues, or about 210,000 miles in the second.

13 See Things not generally Known, p. 88.

14 Some time before the first announcement of the discovery of sun-painting, the following extract from Sir John Herschel’s Treatise on Light, in the EncyclopÆdia Metropolitana, appeared in a popular work entitled Parlour Magic: “Strain a piece of paper or linen upon a wooden frame, and sponge it over with a solution of nitrate of silver in water; place it behind a painting upon glass, or a stained window-pane, and the light, traversing the painting or figures, will produce a copy of it upon the prepared paper or linen; those parts in which the rays were least intercepted being the shadows of the picture.”

15 In his book on Colours, Mr. Doyle informs us that divers, if not all, essential oils, as also spirits of wine, when shaken, “have a good store of bubbles, which appear adorned with various and lively colours.” He mentions also that bubbles of soap and turpentine exhibit the same colours, which “vary according to the incidence of the sight and the position of the eye;” and he had seen a glass-blower blow bubbles of glass which burst, and displayed “the varying colours of the rainbow, which were exceedingly vivid.”

16 The original idea is even attributed to Copernicus. M. Blundevile, in his Treatise on Cosmography, 1594, has the following passage, perhaps the most distinct recognition of authority in our language: “How prooue (prove) you that there is but one world? By the authoritie of Aristotle, who saieth that if there were any other world out of this, then the earth of that world would mooue (move) towards the centre of this world,” &c.

Sir Isaac Newton, in a conversation with Conduitt, said he took “all the planets to be composed of the same matter with the earth, viz. earth, water, and stone, but variously concocted.”

17 Sir William Herschel ascertained that our solar system is advancing towards the constellation Hercules, or more accurately to a point in space whose right ascension is 245° 52' 30, and north polar distance 40° 22'; and that the quantity of this motion is such, that to an astronomer placed in Sirius, our sun would appear to describe an arc of little more than a second every year.—North-British Review, No. 3.

18 See M. Arago’s researches upon this interesting subject, in Things not generally Known, p. 4.

19 This eloquent advocacy of the doctrine of “More Worlds than One” (referred to at p. 51) is from the author’s valuable Outlines of Astronomy.

20 Professor Challis, of the Cambridge Observatory, directing the Northumberland telescope of that institution to the place assigned by Mr. Adams’s calculations and its vicinity on the 4th and 12th of August 1846, saw the planet on both those days, and noted its place (among those of other stars) for re-observation. He, however, postponed the comparison of the places observed, and not possessing Dr. Bremiker’s chart (which would at once have indicated the presence of an unmapped star), remained in ignorance of the planet’s existence as a visible object till the announcement of such by Dr. Galle.

21 For several interesting details of Comets, see “Destruction of the World by a Comet,” in Popular Errors Explained and Illustrated, new edit. pp. 165–168.

22 The letters of Sir Isaac Newton to Dr. Bentley, containing suggestions for the Boyle Lectures, possess a peculiar interest in the present day. “They show” (says Sir David Brewster) “that the nebular hypothesis, the dull and dangerous heresy of the age, is incompatible with the established laws of the material universe, and that an omnipotent arm was required to give the planets their positions and motions in space, and a presiding intelligence to assign to them the different functions they had to perform.”—Life of Newton, vol. ii.

23 The constitution of the nebulÆ in the constellation of Orion has been resolved by this instrument; and by its aid the stars of which it is composed burst upon the sight of man for the first time.

24 Several specimens of Meteoric Iron are to be seen in the Mineralogical Collection in the British Museum.

25 Life of Sir Isaac Newton, vol. i. p. 62.

26 Description of the Monster Telescope, by Thomas Woods, M.D. 4th edit. 1851.

27 This instrument also discovered a multitude of new objects in the moon; as a mountainous tract near Ptolemy, every ridge of which is dotted with extremely minute craters, and two black parallel stripes in the bottom of Aristarchus. Dr. Robinson, in his address to the British Association in 1843, stated that in this telescope a building the size of the Court-house at Cork would be easily visible on the lunar surface.

28 Mr. Hopkins supports his Glacial Theory by regarding the Waves of Translation, investigated by Mr. Scott Russell, as furnishing a sufficient moving power for the transportation of large rounded boulders, and the formation of drifted gravel. When these waves of translation are produced by the sudden elevation of the surface of the sea, the whole mass of water from the surface to the bottom of the ocean moves onward, and becomes a mechanical agent of enormous power. Following up this view, Mr. Hopkins has shown that “elevations of continental masses of only 50 feet each, and from beneath an ocean having a depth of between 300 and 400 feet, would cause the most powerful divergent waves, which could transport large boulders to great distances.”

29 It is scarcely too much to say, that from the collection of specimens of building-stones made upon this occasion, and first deposited in a house in Craig’s Court, Charing Cross, originated, upon the suggestion of Sir Henry Delabeche, the magnificent Museum of Practical Geology in Jermyn Street; one of the most eminently practical institutions of this scientific age.

30 Mr. R. Mallet, F.R.S., and his son Dr. Mallet, have constructed a seismographic map of the world, with seismic bands in their position and relative intensity; and small black discs to denote volcanoes, femaroles, and soltataras, and shades indicating the areas of subsidence.

31 It has been computed that the shock of this earthquake pervaded an area of 700,000 miles, or the twelfth part of the circumference of the globe. This dreadful shock lasted only five minutes; and nearly the whole of the population being within the churches (on the feast of All Saints), no less than 30,000 persons perished by the fall of these edifices.—See Daubeny on Volcanoes; Translator’s note, Humboldt’s Cosmos.

32 Mr. Murray mentions, on the authority of the Rev. Dr. Robinson, of the Observatory at Armagh, that a rough diamond with a red tint, and valued by Mr. Rundell at twenty guineas, was found in Ireland, many years since, in the bed of a brook flowing through the county of Fermanagh.

33 The use of malachite in ornamental work is very extensive in Russia. Thus, to the Great Exhibition of 1851 were sent a pair of folding-doors veneered with malachite, 13 feet high, valued at 6000l.; malachite cases and pedestals from 1500l. to 3000l. a-piece, malachite tables 400l., and chairs 150l. each.

34 Longfellow has written some pleasing lines on “The Fiftieth Birthday of M. Agassiz. May 28, 1857,” appended to “The Courtship of Miles Standish,” 1858.

35 The sloth only deserves its name when it is obliged to attempt to proceed along the ground; when it has any thing which it can lay hold of it is agile enough.

36 Dr. A. Thomson has communicated to Jameson’s Journal, No. 112, a Description of the Caves in the North Island, with some general observations on this genus of birds. He concludes them to have been indolent, dull, and stupid; to have lived chiefly on vegetable food in mountain fastnesses and secluded caverns.

In the picture-gallery at Drayton Manor, the seat of Sir Robert Peel, hangs a portrait of Professor Owen, and in his hand is depicted the tibia of a Moa.

37 According to the law of correlation, so much insisted on by Cuvier, a superior character implies the existence of its inferiors, and that too in definite proportions and constant connections; so that we need only the assurance of one character, to be able to reconstruct the whole animal. The triumph of this system is seen in the reconstruction of extinct animals, as in the above case of the Dinornis, accomplished by Professor Owen.

38 Not only at London, but at Paris, Vienna, Berlin, Turin. St. Petersburg, and almost every other capital in Europe; at Liege, Caen, Montpellier, Toulouse, and several other large towns,—wherever, in fact, there are not great local obstacles,—the tendency of the wealthier inhabitants to group themselves to the west is as strongly marked as in the British metropolis. At Pompeii, and other ancient towns, the same thing maybe noticed; and where the local configuration of the town necessitates an increase in a different direction, the moment the obstacle ceases houses spread towards the west.

39 By far the most complete set of experiments on the Radiation of Heat from the Earth’s Surface at Night which have been published since Dr. Wells’s Memoir On Dew, are those of Mr. Glaisher, F.R.S., Philos. Trans. for 1847.

40 The author is largely indebted for the illustrations in this new field of research to Lieutenant Maury’s valuable work, The Physical Geography of the Sea. Sixth edition. Harper, New York; Low, Son, and Co., London.

41 It is the chloride of magnesia which gives that damp sticky feeling to the clothes of sailors that are washed or wetted with salt water.

42 This fraction rests on the assumption that the dilatation of the substances of which the earth is composed is equal to that of glass, that is to say, 1/18000 for 1°. Regarding this hypothesis, see Arago, in the Annuaire for 1834, pp. 177–190.

43 Electricity, traversing excessively rarefied air or vapours, gives out light, and doubtless also heat. May not a continual current of electric matter be constantly circulating in the sun’s immediate neighbourhood, or traversing the planetary spaces, and exerting in the upper regions of its atmosphere those phenomena of which, on however diminutive a scale, we have yet an unequivocal manifestation in our Aurora Borealis?

44 Could we by mechanical pressure force water into a solid state, an immense quantity of heat would be set free.

45 See Mr. Hunt’s popular work, The Poetry of Science; or, Studies of Physical Phenomena of Nature. Third edition, revised and enlarged. Bohn, 1854.

46 Canton was the first who in England verified Dr. Franklin’s idea of the similarity of lightning and the electric fluid, July 1752.

47 This is mentioned in Procli Diadochi Paraphrasis Ptolem., 1635. (Delambre, Hist. de l’Astronomie ancienne.)

48 The first Variation-Compass was constructed, before 1525, by an ingenious apothecary of Seville, Felisse Guillen. So earnest were the endeavours to learn more exactly the direction of the curves of magnetic declination, that in 1585 Juan Jayme sailed with Francisco Gali from Manilla to Acapulco, for the sole purpose of trying in the Pacific a declination instrument which he had invented.—Humboldt.

49 Gilbert was surgeon to Queen Elizabeth and James I., and died in 1603. Whewell justly assigns him an important place among the “practical reformers of the physical sciences.” He adopted the Copernican doctrine, which Lord Bacon’s inferior aptitude for physical research led him to reject.

50 This illustration, it will be seen, does not literally correspond with the details which precede it.

51 Mr. Crosse gave to the meeting a general invitation to Fyne Court; one of the first to accept which was Sir Richard Phillips, who, on his return to Brighton, described in a very attractive manner, at the Sussex Institution, Mr. Crosse’s experiments and apparatus; a report of which being communicated to the Brighton Herald, was quoted in the Literary Gazette, and thence copied generally into the newspapers of the day.

52 These experiments were performed at the expense of the Royal Society, and cost 10l. 5s. 6d. In the Paper detailing the experiments, printed in the 45th volume of the Philosophical Transactions, occurs the first mention of Dr. Franklin’s name, and of his theory of positive and negative electricity.—Weld’s Hist. Royal Soc. vol. i. p. 467.

53 In this year Andrew Crosse said: “I prophesy that by means of the electric agency we shall be enabled to communicate our thoughts instantaneously with the uttermost parts of the earth.”

54 To which paper the writer is indebted for many of these details.

55 These illustrations have been in the main selected and abridged from papers in the Companion to the Almanac, 1858, and the Penny CyclopÆdia, 2d supp.

56 Newton was, however, much pestered with inquirers; and a Correspondent of the Gentleman’s Magazine, in 1784, relates that he once had a transient view of a Ms. in Pope’s handwriting, in which he read a verified anecdote relating to the above period. Sir Isaac being often interrupted by ignorant pretenders to the discovery of the longitude, ordered his porter to inquire of every stranger who desired admission whether he came about the longitude, and to exclude such as answered in the affirmative. Two lines in Pope’s Ms., as the Correspondent recollects, ran thus:

57 In trying the merits of Harrison’s chronometers, Dr. Maskelyne acquired that knowledge of the wants of nautical astronomy which afterwards led to the formation of the Nautical Almanac.

58 A slight electric shock is given to a man at a certain portion of the skin; and he is directed the moment he feels the stroke to make a certain motion, as quickly as he possibly can, with the hands or with the teeth, by which the time-measuring current is interrupted.

59 Through the calculations of M. Le Verrier.