Chapter V: Appendix: To the List of the Meteorites (3)

[Sidenote: Reproduction of the spectrum of a comet.]

70. Flutings exactly identical with those seen in the spectrum of a comet were obtained by Professor A. W. Wright in 1875[40] on allowing the electric glow to pass through a heated tube, in which, after the introduction of fragments of the Iowa meteorite, the gaseous density had been reduced by an air-pump. The bright lines, too, in the spectrum of a comet, even when nearest to the sun, are found by Sir Norman Lockyer to be identical with those yielded when the electric glow is passed over ordinary meteorites at comparatively low temperatures; and further, the changes in these lines as the comet approaches and recedes from the sun are exactly those which take place on variation of the temperature of the meteorites enclosed in the glow-tubes.

[Sidenote: A comet is perhaps a swarm of meteorites.]

71. From these facts it is inferred that a comet may be in every instance a swarm of isolated large or minute meteorites, at a not very high temperature, shining partly by reflected sunlight and partly by the electric glowing of the gases evolved owing to the action of the sun's heat on the meteorites: further, some of the heat may be due to the clashing together of the meteorites, the grouping of which becomes more and more condensed as the swarm approaches the sun.

The gases driven from the meteorites by the sun's heat would be quite sufficient in quantity to form the tail of the comet: as pointed out by Professor Wright, a meteorite like that which fell at Cold Bokkeveld would furnish 30 cubic miles of gas measured at the pressure of our own atmosphere, and in space itself this gas would expand to enormous dimensions owing to the small mass and attraction of the meteoritic swarm. We are still uncertain, however, as regards the actual physical condition of the matter composing the tail of a comet.

[Sidenote: Saturn's rings are probably swarms of meteorites.]

72. Clerk-Maxwell proved, as long ago as 1857, that the stability of the rings which revolve round the planet Saturn is inconsistent with their being formed of continuous solid or liquid matter; and has shown, by mechanical reasoning, that they must be revolving clouds of small separate bodies, like cannon-shot, each moving as a satellite and almost independent of the rest in its motion: determination of the motions of the inner and outer parts of the ring-system made with the help of the spectroscope supports this conclusion.

[Sidenote: Nebulæ.]

73. Reichenbach, in 1858, before the self-luminosity had been proved by means of the spectroscope, had imagined a nebula to be a cloud of isolated meteorites, illuminated by some neighbouring sun: Chladni, long before, had supposed a nebula to be a cloud of phosphorescent dust. But, in 1864, it was established by Sir William Huggins that the light is due, not to reflection or phosphorescence, but to incandescence, for the spectrum consists of bright lines such as are yielded by glowing gas. Tait,[41] in 1871, suggested that the nebulæ may be clouds of mutually impinging meteorites, mingled with glowing gases developed by the impacts; he pointed out that the heat produced by the clashing of the individuals of such an immense group as a nebula evidently is would be quite adequate for the production of their light. Sir Norman Lockyer finds that the bright lines (generally accompanied by a certain amount of continuous spectrum) which have been observed in nebular spectra are consistent with this suggestion, and regards them as closely related to the low temperature lines obtained when a gentle electric glow is passed over meteorite-fragments in a tube containing gases given out by them, and of which the density has been reduced by the air-pump; further, he points out that the nebular spectrum is identical with that of the comets of 1866 and 1867 when distant from the sun. According to this suggestion, a nebula and a comet are of identical constitution, and a comet is merely a nebula which has become entangled in the solar system. On the other hand, Sir William Huggins has expressed (1891) the opinion that the spectrum of the bright-line nebulæ is certainly not such as we should expect to result from the collision of meteorites like those which have reached the earth, and that it is suggestive of a high temperature; he points out that the particles which have just been in collision may be at high temperatures and yet the average temperature of all the particles may be low.

[Sidenote: Stars.]

74. The examination and classification of the spectra of the stars has likewise led to remarkable conclusions. Secchi, following Rutherfurd, found that the stars could be distributed into classes according to the characters of their spectra,[42] and his classification has since, with little modification, been adopted by Vogel and Dunér, by whom several thousand star-spectra have now been systematically mapped. The first three classes are characterised by absorption, the fourth by radiation.

In the spectra of Class I the absorption is small and simple, the dark lines being broad and few; the stars themselves are white: in one division of this class, represented by Sirius and Vega, the principal lines are due to hydrogen; in another important division, represented by beta, gamma, delta, epsilon, zeta Orionis, lines of helium are very pronounced.

In Class II the dark lines are thinner and more numerous; the stars are bluish-white to reddish-yellow: to this class belong the Sun, Arcturus, Capella.

The absorption in Class III manifests itself predominantly as flutings, though there are also many thin lines: the stars are orange or red: in one division (a) of this class the darkest part and the sharpest edge of each fluting is towards the violet end of the spectrum, as in Betelgeux; in a smaller division (b) the darkest part of each fluting is towards the red end, as in star 152 Schjellerup; the fluting absorption of the latter division being due to carbon.

The remaining Class IV is an extremely small one: the spectra are characterised by bright lines: some of the lines are due to hydrogen, and others to substances not yet recognised in terrestrial chemistry.

[Sidenote: Supposed cooling of all the stars.]

75. Soon after the classification suggested by Secchi had been announced, it was surmised that the differences in the stars of the first three classes might be due, not so much to differences of matter, as to differences of temperature, and that a very hot star such as, from its brightness and distance, its small and simple absorption, and the development of the blue end of its spectrum, Vega is believed to be, would, on getting older and colder, pass from Class I to Class II, and thence to one or other of the divisions of Class III.

[Sidenote: New stars.]

76. In 1866 a star of 9th or 10th magnitude burst into greater brilliancy and nearly reached the intensity of Vega; the spectrum showed the presence of brilliantly glowing hydrogen. Almost as suddenly the light went down again, and within a month returned to its original brightness. Ten years later, another new star of the 3rd or 4th magnitude appeared at a place in the sky where no star had been noticed before; its spectrum showed numerous bright lines; gradually, in the course of a year, it dwindled down to the 10th magnitude, then giving the telescopic appearance and the spectrum of a nebula. Several other new stars have since been observed, the most notable being Nova Persei, which appeared in 1901. In each case, as the star faded, its spectrum changed into that which is characteristic of the nebulæ.

The appearance of a new star has been generally attributed to the collision of two bodies in space; Sir Norman Lockyer[43] has pointed out that the rapidity of the change in the brilliancy, so different from that of other stars, may be due to the smallness of the mass, and that such a star may be produced by the collision of two swarms of widely separated meteorites. He has shown that the changes in the spectrum as such a star varies in brightness are confirmatory of this view.

[Sidenote: The heat of the sun.]

77. That the heat of our own sun was originated by the falling together of smaller bodies was, until lately, generally acknowledged;[44] for the only other conceivable natural cause, known to exist from independent evidence, namely, chemical combination, was quite insufficient; the greatest amount of heat obtainable from the most advantageous chemical combination of any of the then known elements, having a total mass equal to that of the sun, would not cover the sun's expenditure for more than three thousand years, while there is no difficulty on the meteoritic explanation in providing a supply of heat sufficient to cover the loss by radiation during 20,000,000 years. But the discovery that compounds of radium maintain themselves at a higher temperature than that of surrounding bodies and are only inappreciably changed though continuously emitting an appreciable amount of heat, shows that the meteoritic hypothesis as to the cause of the sun's high temperature is not necessarily the true one: there may be an analogous heat-yielding material in the sun.

In any case the present loss of the sun's heat by radiation is probably not covered by the fall of bodies into the sun; for the requisite mass would, if from distant regions, visibly affect the motions of the planets by its attraction, and, even if circulating round the sun at no great distance from it, would seriously disturb the motions of some of the comets. Further, much heat will result from the shrinkage of the volume of the solar aggregate.

[Sidenote: Evolution of the heavenly bodies.]

78. By study of the spectra, at various temperatures, of the elements and compounds found in those meteorites which have reached our earth and been preserved, Sir Norman Lockyer[45] has been led to support the view that the stars are not at present all cooling down, but that some, on the contrary, are rising in temperature; he suggests that many of the stars, like the nebulæ, are constituted of separate meteorites in continual relative motion, and become hotter and hotter through contraction of the grouping, collision, and transformation of the energy of position and motion into heat. This increase of temperature must continue during successive ages, until the energy of position and motion of the separate meteorites is wholly transformed, the separate masses having then combined to form a single white hot body which will gradually cool down to the state in which our own moon now is. If a swarm of meteorites forming one nebula be subjected to the external action of another moving swarm of meteorites, intermediate stages resembling the conditions of Saturn and of the solar system may ensue.

According to this spectroscopic affirmation of the nebular theory, all the heavenly bodies are constituted of the same kinds of elementary matter, those in fact which are found in meteorites and our own earth, and the difference is solely due to temperature; and a nebula in its gradual passage to the lunar condition will show every phase of spectrum observed in the stars as now existent.

* * * * *

[Sidenote: Meteorites present no evidence of life.]

79. Finally, it may be asked whether or not meteorites bring us any tangible evidence of the existence of living beings outside our own world. To this we may briefly answer, that while an organic origin can scarcely be claimed for the graphite present in the meteoric irons, there are no less than six meteoric stones which contain, though in very minute quantity, carbon compounds of such a character that their presence in a terrestrial body would be regarded as doubtlessly an indirect result of animal or vegetable existence. On the other hand, the stony matter is such that in a terrestrial body an igneous origin would be assumed.

Professor Maskelyne has pointed out that these carbon compounds can be completely removed without a preliminary pulverisation of the stone, and thus seem to be contained merely in the pores; he suggested that they may have been absorbed by the stones in their passage through an atmosphere containing the compounds in a state of vapour. In any case, it is impossible to prove that there is a necessary relation between these compounds of carbon and the existence of living beings.

[Sidenote: Chondrules have been mistaken for organisms.]

80. In 1880[46] descriptions were given of sponges, corals, crinoids and plants, found in several meteorites, chiefly in that of Knyahinya, but the memoir has been generally regarded as an elaborate jest. The chondrules with their excentrically radiating crystallisation are there classified and named as sponges, corals and crinoids, while the structure of meteoric iron, revealed by the Widmanstätten figures, is regarded as a result of plant life. There can be no hesitation in asserting that as yet no organised matter has been found in meteorites.

FOOTNOTES:

[1] Remarks concerning stones said to have fallen from the clouds both in these days and in ancient times: by Edward King. London, 1796. Mémoire historique et physique sur les chutes des pierres: par P. M. S. Bigot de Morogues. Orléans, 1812.

[2] Sitzungsber. d. k. Ak. d. Wiss. Wien. 1856, vol. 22, p. 393.

[3] Records of the Geological Survey of India. Calcutta, 1885, vol. 18, p. 237.

[4] Ueber den Ursprung der von Pallas gefundenen und anderer ihr ähnlicher Eisenmassen. Riga, 1794.

[5] Reise durch verschiedene Provinzen des russischen Reichs: von P. S. Pallas. St. Petersburg, 1776, Part III., p. 411.

[6] Philosophical Transactions. London, 1788, vol. 78, part 1, pp. 37, 183.

[7] Philosophical Transactions. London, 1795, vol. 85, p. 103.

[8] _Ibid._, 1802, vol. 92, p. 174.

[9] Bulletin des Sciences par la Société Philomathique. Paris, 1803, vol. 3, no. 71, p. 180.

[10] Mémoires de l'Institut National de France. 1806, vol. 7, part 1, Histoire, p. 224.

[11] Principes de Thermodynamique: par Paul de Saint-Robert. Paris, 1870, p. 329.

[12] The Fall of Butsura: by Prof. Maskelyne. Phil. Mag. 1863, vol. 25, p. 50.

[13] Die chemische Natur der Meteoriten: von C. Rammelsberg. Berlin, 1870-9. Météorites: par S. Meunier. Paris, 1884. Meteoritenkunde: von E. Cohen. Stuttgart, 1894-1905.

[14] Some lecture-notes on meteorites: by Prof. Maskelyne. _Nature_, 1875, vol. 12, pp. 485, 504, 520.

[15] Études synthétiques de géologie expérimentale. Paris, 1879. p. 517.

[16] Phil. Mag. 1884, ser. 5, vol. 17, p. 462.

[17] _Nature_, 1904, vol. 71, p. 32.

[18] Neues Jahrbuch für Mineralogie, 1905, Band I, p. 122.

[19] Denksch. d. math-naturw. Klasse d. k. Ak. d. Wiss., 1905, Band 78, p. 635.

[20] Philosophical Transactions, London, 1908, Ser. A, vol. 208, p. 21.

[21] Mineralogical Magazine. London, 1884, vol. 6, p. 1.

[22] Beschreibung und Eintheilung der Meteoriten. Berlin, 1864.

[23] Die mikroskopische Beschaffenheit der Meteoriten: von G. Tschermak. Stuttgart, 1883-5.

[24] Pogg. Ann. 1858, vol. 105, p. 438: Phil. Mag. 1876, ser. 5, vol. 1, p. 497.

[25] On the structure and origin of meteorites. _Nature_, 1877, vol. 15, p. 495.

[26] Die Meteoritensammlung d.k.k. min. Hofkabinetes in Wien. 1885, p. 19.

[27] Lithological Studies. Cambridge, U.S.A. 1884, p. 110.

[28] Speculations on the source of Meteorites. _Nature_, 1879, vol. 19, p. 493.

[29] _Olmsted._ American Jour. Sc., 1834, ser. 1, vol. 25, p. 363.

[30] _Newton._ American Jour. Sc., 1864, ser. 2, vol. 37, p. 377; vol. 38, p. 53.

[31] Report Brit. Assoc., 1868, p. 394.

[32] Pogg. Ann., 1858, vol. 105, p. 438.

[33] Denning. _Nature_, 1885, vol. 31, p. 463.

[34] Monthly Notices of the Roy. Astron. Soc. 1899, vol. 59, p. 179.

[35] Newton. _Nature_, 1886, vol. 33, pp. 392, 418.

[36] _Newton._ American Jour. Sc., 1886, ser. 3, vol. 31, p. 409.

[37] _Hidden._ American Jour. Sc., 1887, ser. 3, vol. 33, p. 223.

[38] Presidential Address to the Brit. Assoc. for the Advancement of Science, 1891.

[39] Proc. Roy. Soc., Edinb., 1869, vol. 6, p. 553.

[40] American Jour. Sc., 1875, ser. 3, vol. 10, p. 44.

[41] Proc. Roy. Soc., Edinb., 1871, vol. 7, p. 460.

[42] Lockyer. _Nature_, 1886, vols. 33 and 34.

[43] _Nature_, 1877, vol. 16, p. 413.

[44] Treatise on Natural Philosophy, by Thomson and Tait: _Cambridge_, 1883, vol. 1, part 2, p. 487.

[45] Proc. Royal Society, 1887, vol. 43, p. 117: 1888, vol. 44, Bakerian lecture.

[46] Die Meteorite (Chondrite) und ihre Organismen: von Dr. O. Hahn. Tübingen, 1880.

LIST OF THE METEORITES

REPRESENTED IN THE COLLECTION
ON MAY 1, 1908.

* * * * *

_The references in the second column correspond with numbers and
letters on the cases, and indicate the pane behind which the meteorite
will be found._

* * * * *

Weights under one gram are not given. 1,000 grams are equivalent to
2·205 avdp. lbs.

* * * * *