Chapter XIV: Part II: A Couple of Centuries' Progress (6)

Evolution is always a slow process. To evolve such an animal as a greyhound from its remote ancestors, according to Mr. Darwin, needs immense tracts of time; and if the evolution of some feeble animal crawling on the surface of this planet is slow, shall the stately evolution of the planetary orbs themselves be hurried? It may be that we are able to trace the history of the solar system for some thousand million years or so; but for how much longer time must it not have a history--a history, and also a future--entirely beyond our ken?

Those who study the stars have impressed upon them the existence of the most immeasurable distances, which yet are swallowed up as nothing in the infinitude of space. No less are we compelled to recognize the existence of incalculable æons of time, and yet to perceive that these are but as drops in the ocean of eternity.

FOOTNOTES:

[1] The following account of Mars's motion is from the excellent small manual of astronomy by Dr. Haughton of Trinity College, Dublin:--(P. 151) "Mars's motion is very unequal; when he first appears in the morning emerging from the rays of the sun, his motion is direct and rapid; it afterwards becomes slower, and he becomes stationary when at an elongation of 137° from the sun; then his motion becomes retrograde, and its velocity increases until he is in opposition to the sun at 180°; at this time the retrograde motion is most rapid, and afterwards diminishes until he is 137° distant from the sun on the other side, when Mars again becomes stationary; his motion then becomes direct, and increases in velocity until it reaches a maximum, when the planet is again in conjunction with the sun. The retrograde motion of this planet lasts for 73 days: and its arc of retrogradation is 16°."

[2] It is not so easy to plot the path of the sun among the stars by direct observation, as it is to plot the path of a planet; because sun and stars are not visible together. Hipparchus used the moon as an intermediary; since sun and moon are visible together, and also moon and stars.

[3] This is, however, by no means the whole of the matter. The motion is not a simple circle nor has it a readily specifiable period. There are several disturbing causes. All that is given here is a first rough approximation.

[4] The proof is easy, and ought to occur in books on solid geometry. By a "regular" solid is meant one with all its faces, edges, angles, &c., absolutely alike: it is of these perfectly symmetrical bodies that there are only five. Crystalline forms are practically infinite in number.

[5] Best known to us by his Christian name, as so many others of that time are known, _e.g._ Raphael Sanzio, Dante Alighieri, Michael Angelo Buonarotti. The rule is not universal. Tasso and Ariosto are surnames.

[6] It would seem that the fact that all bodies of every material tend to fall at the same rate is still not clearly known. Confusion is introduced by the resistance of the air. But a little thought should make it clear that the effect of the air is a mere disturbance, to be eliminated as far as possible, since the atmosphere has nothing to do with gravitation. The old fashioned "guinea and feather experiment" illustrates that in a vacuum things entirely different in specific gravity or surface drop at the same pace.

[7] Karl von Gebler (Galileo), p. 13.

[8] It is of course the "silver lining" of clouds that outside observers see.

[9] L.U.K., _Life of Galileo_, p. 26.

[10] _Note added September, 1892._ News from the Lick Observatory makes a very small fifth satellite not improbable.

[11] They remained there till this century. In 1835 they were quietly dropped.

[12] It was invented by van Helmont, a Belgian chemist, who died in 1644. He suggested two names _gas_ and _blas_, and the first has survived. Blas was, I suppose, from _blasen_, to blow, and gas seems to be an attempt to get at the Sanskrit root underlying all such words as _geist_.

[13] Such as this, among many others:--The duration of a flame under different conditions is well worth determining. A spoonful of warm spirits of wine burnt 116 pulsations. The same spoonful of spirits of wine with addition of one-sixth saltpetre burnt 94 pulsations. With one-sixth common salt, 83; with one-sixth gunpowder, 110; a piece of wax in the middle of the spirit, 87; a piece of _Kieselstein_, 94; one-sixth water, 86; and with equal parts water, only 4 pulse-beats. This, says Liebig, is given as an example of a "_licht-bringende Versuch_."

[14] Draper, _History of Civilization in Europe_, vol. ii. p. 259.

[15] Professor Knight's series of Philosophical Classics.

[16] To explain why the entire system, horse and cart together, move forward, the forces acting on the ground must be attended to.

[17] The distance being proportional to the _square_ of the time, see p. 82.

[18] The following letter, recently unearthed and published in _Nature_, May 12, 1881, seems to me well worth preserving. The feeling of a respiratory interval which it describes is familiar to students during the too few periods of really satisfactory occupation. The early guess concerning atmospheric electricity is typical of his extraordinary instinct for guessing right.

"LONDON, _Dec. 15, 1716_.

"DEAR DOCTOR,--He that in ye mine of knowledge deepest diggeth, hath, like every other miner, ye least breathing time, and must sometimes at least come to terr. alt. for air.

"In one of these respiratory intervals I now sit down to write to you, my friend.

"You ask me how, with so much study, I manage to retene my health. Ah, my dear doctor, you have a better opinion of your lazy friend than he hath of himself. Morpheous is my last companion; without 8 or 9 hours of him yr correspondent is not worth one scavenger's peruke. My practices did at ye first hurt my stomach, but now I eat heartily enou' as y' will see when I come down beside you.

"I have been much amused at ye singular [Greek: _phenomena_] resulting from bringing of a needle into contact with a piece of amber or resin fricated on silke clothe. Ye flame putteth me in mind of sheet lightning on a small--how very small--scale. But I shall in my epistles abjure Philosophy whereof when I come down to Sakly I'll give you enou'. I began to scrawl at 5 mins. from 9 of ye clk. and have in writing consmd. 10 mins. My Ld. Somerset is announced.

"Farewell, Gd. bless you and help yr sincere friend.

"ISAAC NEWTON.

"_To_ DR. LAW, Suffolk."

[19] Kepler's laws may be called respectively, the law of path, the law of speed, and the relationship law. By the "mass" of a body is meant the number of pounds or tons in it: the amount of matter it contains. The idea is involved in the popular word "massive."

[20] The equation we have to verify is

4[pi]^2r^3
gR^2 = -----------,
T^2

with the data that _r_, the moon's distance, is 60 times R, the earth's radius, which is 3,963 miles; while T, the time taken to complete the moon's orbit, is 27 days, 13 hours, 18 minutes, 37 seconds. Hence, suppose we calculate out _g_, the intensity of terrestrial gravity, from the above equation, we get

4[pi]^2 39·92 × 216000 × 3963 miles
_g_ = ---------- × (60)^3R = -----------------------------
T (27 days, 13 hours, &c.)^2

= 32·57 feet-per-second per second,

which is not far wrong.

[21] The two motions may be roughly compounded into a single motion, which for a few centuries may without much error be regarded as a conical revolution about a different axis with a different period; and Lieutenant-Colonel Drayson writes books emphasizing this simple fact, under the impression that it is a discovery.

[22] Members of the Accademia dei Lyncei, the famous old scientific Society established in the time of Cosmo de Medici--older than our own Royal Society.

[23] Newton suspected that the moon really did so oscillate, and so it may have done once; but any real or physical libration, if existing at all, is now extremely minute.

[24] An interesting picture in the New Gallery this year (1891), attempting to depict "Earth-rise in Moon-land," unfortunately errs in several particulars. First of all, the earth does not "rise," but is fixed relatively to each place on the moon; and two-fifths of the moon never sees it. Next, the earth would not look like a map of the world with a haze on its edge. Lastly, whatever animal remains the moon may contain would probably be rather in the form of fossils than of skeletons. The skeleton is of course intended as an image of death and desolation. It is a matter of taste: but a skeleton, it seems to me, speaks too recently of life to be as appallingly weird and desolate as a blank stone or ice landscape, unshaded by atmosphere or by any trace of animal or plant life, could be made.

[25] Five of Jupiter's revolutions occupy 21,663 days; two of Saturn's revolutions occupy 21,526 days.

[26] _Excircularity_ is what is meant by this term. It is called "excentricity" because the foci (not the centre) of an ellipse are regarded as the representatives of the centre of a circle. Their distance from the centre, compared with the radius of the unflattened circle, is called the excentricity.

[27] A curve of the _n_th degree has 1/2_n_(_n_+3) arbitrary constants in its equation, hence this number of points specifically determine it. But special points, like focus or vertex, count as two ordinary ones. Hence three points plus the focus act as five points, and determine a conic or curve of the second degree. Three observations therefore fix an orbit round the sun.

[28] Its name suggests a measure of the diameter of the sun's disk, and this is one of its functions; but it can likewise measure planetary and other disks; and in general behaves as the most elaborate and expensive form of micrometer. The Königsberg instrument is shewn in fig. 92.

[29] It may be supposed that the terms "minute" and "second" have some necessary connection with time, but they are mere abbreviations for _partes minutæ_ and _partes minutæ secundæ_, and consequently may be applied to the subdivision of degrees just as properly as to the subdivision of hours. A "second" of arc means the 3600th part of a degree, just as a second of time means the 3600th part of an hour.

[30] A group of flying particles, each one invisible, obstructs light singularly little, even when they are close together, as one can tell by the transparency of showers and snowstorms. The opacity of haze may be due not merely to dust particles, but to little eddies set up by radiation above each particle, so that the air becomes turbulent and of varying density. (See a similar suggestion by Mr. Poynting in _Nature_, vol. 39, p. 323.)

[31] The moon ought to be watched during the next great shower, if the line of fire happens to take effect on a visible part of the dark portion.

[32] Address to Birmingham Midland Institute, "A Glimpse through the Corridors of Time."

INDEX

INDEX

A

Abbott, T.K., on tides, 369

Adams, John Couch, 193, 217, 302, 323, 324, 325, 327, 329, 330, 352, 385

Airy, Sir George, 193, 244, 302, 323, 324, 327, 367

Anaxagoras, 15

Appian, 218

Arabs, the, form a link between the old and new science, 9

Archimedes, 7, 8, 84, 87, 144, 177

Aristarchus, 34

Aristotle, 66, 69, 88, 94, 99, 167.
He taught that the earth was a sphere, 16;
his theories did not allow of the earth's motion, 34;
he was regarded as inspired, 89

B

Bacon, Francis, 142, 143, 144, 145.
His _Novum Organum_, 141

Bacon, Roger, 96, 139, 140.
The herald of the dawn of science, 9

Brahé, George, uncle of Tycho Brahé, 39

Brahé, Steno, brother of Tycho Brahé, 39

Brahé, Tycho, 37, 39, 40, 44, 45, 49, 51, 53, 54, 55, 58, 63, 64, 65, 66,
68, 71, 72, 74, 75, 77, 78, 86, 94, 117, 137, 155, 165, 166, 200, 244,
281, 288.
He tried to adopt the main features of the Copernican theory without
admitting the motion of the earth, 37;
he was a poor theorist but a great observer, 38;
his medicine, 44;
his personal history, 39, _seq._;
his observatory, Uraniburg, 47;
his greatest invention, 50, note;
his maniac Lep, 52;
his kindness to Kepler, 63

Ball, Sir R., 391, 394;
his _Story of the Heavens_, 377

Barrow, Dr., 165, 187

Bessel, 288, 310, 311, 313, 315, 316, 318, 323

Biela, 345, 346, 347

Bode's Law, 60, 296, 298, 299, 326

Boyle, 139, 188

Bradley, Prof. James, 233, 246, 247, 249, 252, 253, 308, 319

Bremiker, 328, 329

Brewster, on Kepler, 78

Brinkley, 308

Bruno, Giordano, 108, 127

C

Castelli, 112, 133

Cayley, Prof., 385

Challis, Prof., 328, 329

Clairut, 193, 216, 217, 219, 234, 341

Clark, Alvan and Sons, 316

Columbus, 9, 144

Copernicus, 7, 10, _seq._, 14, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38,
62, 66, 68, 70, 78, 93, 95, 100, 108, 111, 121, 122, 137, 155, 166, 223,
234, 247, 307;
his _De Revolutionibus Orbium Coelestium_, 11, 75, 138;
he _proved_ that the earth went round the sun, 13;
the influence of his theory on the Church, 13, _seq._;
his life-work summarised, 30;
his Life by Mr. E.J.C. Morton, 31

Copernican tables, 40;
Copernican theory, 59, 60, 125, 144, 167

Copernik, Nicolas; see Copernicus

Cornu, 238

Croll, Dr., his _Climate and Time_, 264

D

D'Alembert, 193, 234

Darwin, Charles, 134, 138, 397

Darwin, Prof. George, 367, 394

Delambre, 253

Descartes, 145, 146, 148, 151, 153, 156, 158, 164, 165, 167, 178, 181,
224, 227;
his _Discourse on Method_, 142;
his dream, 147;
his system of algebraic geometry, 149, _seq._;
his doctrine of vortices, 151, _seq._;
his _Principia Mathematica_, 154;
his Life by Mr. Mahaffy, 154

E

Earth, the difficulties in the way of believing that it moved, 34, _seq._

"Earth-rise in Moon-land," 258, note

Encke, 345, 346

Epicyclic orbits explained, 23, _seq._

Equinoxes, their precession discovered by Hipparchus, 27

Eudoxus, 19

Euler, 193, 234

F

Faraday, 84

Fizeau, 238, 239

Flamsteed, 215, 246, 284, 308, 319

Fraunhofer, 311

Froude, Prof.; his _Oceania_, 387

G

Galen, 87

Galileo, Galilei, 63, 75, 84, 88, 90, 92, 93, 97, 98, 101, 104, 106, 107,
108, 109, 110, 112, 114, 116, 117, 118, 120, 121, 122, 123, 125, 127,
133, 134, 137, 144, 145, 153, 154, 157, 165, 166, 167, 168, 177, 188,
200, 224, 227, 256, 281, 288, 309, 361;
his youth, 85;
his discovery of the pendulum, 86;
his first observations about falling bodies, 88, _seq._;
he invents a telescope, 95;
he adopts the Copernican theory, 94;
he conceives "earth-shine," 100;
he discovers Jupiter's moons, 103;
he studies Saturn, 114, _seq._;
his _Dialogues on the Ptolemaic and Copernican Systems_, 124;
his abjuration, 130;
he becomes blind, 132;
he discovered the Laws of Motion, 167, _seq._;
he guessed that sight was not instantaneous, 236, 237

Galle, Dr., 245, 329

Gauss, 299, 300

Gilbert, Dr., 139, 140, 157, 188;
his _De Magnete_, 140, 144

Greeks, their scientific methods, 7

Groombridge's Catalogue, 315

H

Hadley, 185

Halley, 192, 193, 194, 195, 197, 215, 218, 219, 246, 258, 260, 261, 340, 341; he discovered the _Principia_, 194

Harvey, 144, 149

Haughton, Dr., 321;
his manual on Astronomy, 21, note

Heliometer, described, 311

Helmholtz, 378

Helmont, Van, invented the word "gas," 141

Henderson, 310, 314

Herschel, Alexander, 275, 277, 278, 279

Herschel, Caroline, 275, 276, 279, 286, 345;
her journal quoted, 277, _seq._;
her work with William H. described, 284

Herschel, Sir John, 283, 285, 327, 329

Herschel, William, 185, 234, 235, 244, 249, 274, 275, 280, 281, 282, 284,
288, 289, 290, 293, 295, 305, 309, 310, 318, 319, 327;
he "sweeps" the heavens, 280;
his discovery of Uranus, 281, 287;
his artificial Saturn, 281, 282;
his methods of work with his sister, described, 284;
he founded the science of Astronomy, 287

Hind, 300

Hipparchus, 7, 18, 20, 27, 28, and note, 30, 40, 66, 223, 253;
an explanation of his discovery of the precession of the equinoxes,
27, seq.

Hippocrates, 87

Homeric Cosmogony, 15, _seq._

Hooke, 139, 188, 192, 193, 196, 197, 308

Hôpital, Marquis de l', 228

Horkey, Martin, 106

Horrebow, 244

Huxley, Prof., 149

Huyghens, 86, 166, 185

K

Kant, 267, 270

Kelvin, Lord, see Thomson, Sir W.

Kepler, John, 59, 60, 63, 64, 65, 66, 70, 72, 73, 75, 77, 79, 84, 93,
94, 95, 104, 106, 107, 110, 122, 137, 145, 153, 158, 164, 165, 166,
167, 192, 200, 208, 209, 210, 211, 212, 214, 218, 224, 227, 253, 256,
259, 260, 262, 288, 295, 296, 332, 338, 361, 389;
he replaced epicycles by an ellipse, 27;
he was a pupil of Tycho Brahé, 54;
he was a speculator more than an observer, 58;
his personal life, 58, _seq._;
his theories about the numbers and distances of the planets, 60, 62;
he was helped by Tycho, 63;
his main work, 65, _seq._;
he gave up circular motion, 69;
his _Mysterium Cosmographicon_, 105;
his Laws, 71, 74, 173, 174, 176, 179, 180, 206, _seq._

L

Lagrange, 193, 234, 255, 256, 257, 258, 263

Lagrange and Laplace, 258, 266, 395;
they laid the foundations of the planetary theory, 259

Laplace, 68, 193, 218, 234, 255, 261, 262, 267, 268, 269, 270, 272,
288, 301, 317, 384, 385, 390;
his nebular hypothesis, 267, 292;
his _Mécanique Céleste_, 323

Lassell, Mr., 283, 284

Leibnitz, 192, 197, 233

Le Monnier, 319

Leonardo, see Vinci, Leonardo da

Leverrier, 193, 327, 328, 329, 330, 352

Lippershey, Hans, 95

M

Maskelyne, 281

Maxwell, Clerk, 302, 303

Molyneux, 248, 249

Morton, Mr. E.J. C, his Life of Copernicus, 31

N

Newton, Prof. H.A., 347

Newton, Sir Isaac, 7, 30, 79, 138, 139, 144, 145, 149, 153, 157, 158,
165, 166, 167, 174, 176, 184, 187, 188, 189, 191, 192, 194, 196, 198,
199, 201, 213, 216, 219, 220, 221, 224, 226, 227, 228, 233, 242, 253,
255, 256, 274, 288, 317, 340, 378;
his _Principia_, 191, 192, 193, 194, 195, 196, 197, 207, 214, 216, 218,
228, 233, 242, 253;
his early life, 161, _seq._;
his first experiments, 163;
his work at Cambridge, 164;
his Laws, 168;
his application of the Laws of Gravity to Astronomy, 177, 178, 179, 185,
190;
his reticence, 178;
his discoveries in Optics, 181, _seq._;
his work summarised, 186;
his _Optics_, 189;
anecdotes of him, 191;
his appearance in a Court of Justice, 195;
some of his manuscripts very recently discovered, 217;
his theories of the Equinoxes and tides, 223, _seq._, 225, 363, _seq._

O

Olbers, 299, 300

P

Peters, Prof., 300, 316

Piazzi, 298, 299, 308, 313

Picard, 190, 242, 244, 247

Pioneers, genuine, 7

Planets and days of the week, 18

Poynting, 332

Printing, 9

Ptolemy, 18, 20, 27, 38, 153, 155, 166, 214;
his system of the Heavens simplified by Copernicus, 11, 30;
his system described, 19, _seq._;
his system taught, 34;
his harmonies, 74

Pythagoras, 19, 20, 34

Q

Quadrant, an early, 42, 43

R

Rheiter, 107

Ricci, Ostillio, 86, 87

Roberts, Isaac, 268

Roemer, 239, 240, 242, 244, 249, 251, 308

Rosse, Lord, his telescope, 186, 268

Rudolphine tables, 65

S

Scheiner, 107

Sizzi, Francesca, an orthodox astronomer, 106

Snell, Willebrod, and the law of refraction, 65

Solar system, its fate, 265

Stars, a list of, 307

Struve, 308, 310, 311, 313

Stuart, Prof., quoted, 52

T

Tatius, 296

Telescopes, early, 96

Thales, 7, 140, 317

Thomson, Sir William, 367, 372, 373, 378, 394

Tide-gauge, described, 373, _seq._

Tides, 354, _seq._

Time, is not exactly uniform, 384

Torricelli, 133, 168

Tycho, see Brahé, Tycho

V

Vinci, Leonardo da, 9, 100, 144, 184

Viviani, 133, 168

Voltaire, 181

W

Watson, Prof., 300

Whewell, 227

Wren, Sir Christopher, 188, 192, 193, 197

Z

Zach, Von, 296, 299

Zone of Asteroids, 300, _seq._

THE END.

RICHARD CLAY AND SONS, LIMITED, LONDON AND BUNGAY.