Recalling to mind the remarkable interview between Newton and Conduit at Kensington,* I would ask why the elementary substances that compose one group of cosmical bodies, or one planetary system, may not, in a great measure, be identical?
[footnote] * "Sir Isaac Newton said he took all the planets to be composed of the same matter with the Earth, viz., earth, water, and stone, but variously connected." — Turner, 'Collections for the History of Grantham, containing authentic Memoirs of Sir Isaac Newton', p. 172.
Why should we not adopt this view, since we may conjecture that these planetary bodies, like all the larger or smaller agglomerated masses revolving round the sun, have been thrown off from the once far more expanded solar atmosphere, and been formed from vaporous rintgs describing their orbits round the central body? We are not, it appears to me, more justified in applying the term telluric to the nickel and iron, the olivine and pyroxene (augite), found in meteoric stones, than in indicating the German plants which I found beyond the Obi as European species of the flora of Northern Asia. If the elementary substances composing a group of cosmical bodies of different magnitudes be identical, why should they not likewise, in obeying the laws of mutual attraction, blend together under definite relations of mixture, composing the white glittring snow and ice in the polar zones of the planet Mars, or constituting in the smaller cosmical masses mineral bodies inclosing crystals of olivine, augite, and labradorite? Even in the domain of pure conjecture we should not suffer ourselves to be led away by unphilosophical and arbitrary views devoid of the support of inductive reasoning.
Remarkable obscurations of the sun's disk, during which the stars have been seen at mid-day (as, for instance, in the obscuration of 1547, which continued for three days, and occurred about the time of the eventful battle of Mühlberg), can not be explained as arising from volcanic ashes or mists, and were regarded by Kepler as owing either to a 'materia cometica', or to a black cloud formed by the sooty exhalations of the solar body. The shorter obscurations of 1090 and 1203, which continued, the one only three, and the other six p 133 hours, were supposed by Chladni and Schnurrer to be occasioned by the passage of meteoric masses before the sun's disk. Since the period that streams of meteoric shooting stars were first considered with reference to the direction of their orbit as a closed ring, the epochs of these mysterious celestial phenomena have been observed to present a remarkable connection with the regular recurrence of swarms of shooting stars Adolph Erman has evinced great acuteness of mind in his accurate investigation of the facts hitherto observed on this subject, and his researches have enabled him to discover the connection of the sun's conjunction with the August asteroids on the 7th of February, and with the November asteroids on the 12th of May, the latter period corresponding with the days of St. Mamert (May 11th), St. Pancras (May 12th), and St. Servatius (May 13th), which according to popular belief, were accounted "cold days."*
[footnote] Adolph Erman, in Poggend., 'Annalen', 1839, bd. xlviii., s. 582-601. Biot had previously thrown doubt regarding the probability of the November stream reappearing in the beginning of May ('Comptes Rendus', 1836, t. ii., p. 670). Mädler has examined the mean depression of temperature on the three ill-named days of May by Berlin observations for eighty-six years ('Verhandl. des Vereins zur Bedförd, des Gartenbaues', 1834, s. 377), and found a retrogression of temperature amounting to 2.2 degrees Fahr. from the 11th to the 13th of May, a period at which nearly the most rapid advance of heat takes place. It is much to be desired that this phenomenon of depressed temperature, which some have felt inclined to attribute to the melting of the ice in the northeast of Europe, should be also investigated in very remote spots, as in America, or in the southern hemisphere. (Comp. 'Bull. de l'Acad. Imp. de St. Pétersbourg', 1843, t. i., No. 4.)
The Greek natural philosophers, who were but little disposed to pursue observations, but evinced inexhaustible fergility of imagination in giving the most various interpretation of half-perceived facts, have, however, left some hypotheses regarding shooting stars and meteoric stones which strikingly accord with the views now almost universally admitted of the cosmical process of these phenomena. "Falling stars," says Plutarch, in his life of Lysander,* are, according to the opinion of some physicists, not eruptions of the ethereal fire extinguished in the air immediately after its ignition, nor yet an inflammatory combustion of the air, which is dissolved in large quantities in the upper regions of space, but these meteors are rather a fall of celestial bodies, which, in consequence of a certain intermission in the rotatory force, and by the impulse of some irregular movements, have been hurled down not only to the inhabited portions of the Earth, but also beyond it into the great ocean, where we can not find them."
[footnote] *Plut., 'Vitæ par, in Lysandro', cap. 22. The statement of Damachos (Daïmachos), that for seventy days continuously there was a fiery cloud seen in the sky, emitting sparks like falling stars, and which then, sinking nearer to the earth, let fall the stone of Ægos Potamos, "which, however, was only a small part of it," is extremely improbable, since the direction and velocity of the fire-cloud would in that case of necessity have to remain for so many days the same as those of the earth; and this, in the fire-ball of the 19th of July, 1686, described by Halley ('Trans.', vol. xxix., p. 163), lasted only a few minutes. It is not altogether certain whether Daïmachos, the writer, [Greek words], was the same person as Daïmachos of Platæa, who was sent by Selencus to India to the son of Androcottos, and who ws charged by Strabo with being "a speaker of lies" (p. 70, Casaub.). From another passage of Plutarch ('Compar. Solonis c. Cop.', cap. 5) we should almost believe that he was. At all events, we have here only the evidence of a very late author, who wrote a century and a half after the fall of aërolites occurred in Thrace, and whose authenticity is also doubted by Plutarch.
Diogenes of Apollonia* expresses himself still more explicitly.
[footnote] *Stob., ed. Heeren, i., 25, p. 508; Plut., 'de plac. Philos.', ii., 13.
According to his views, "Stars that are 'invisible', and, consequently, have no name, move in space together with those that are visible. These invisible stars frequently fall burning at Ægos Potamos." The Apollonian, who held all other stellar bodies, when luminous, to be of a pumice-like nature, probably grounded his opinions regarding shooting stars and meteoric masses on the doctrine of Anaxagoras the Clazomenian, who regarded all the bodies in the universe "as fragments of rocks, which the fiery ether, in the force of its gyratory motion, had torn from the Earth and converted into stars." In the Ionian school, therefore, according to the testimony transmitted to us in the views of Diogenes of Apollonia, aërolites and stars were ranged in one and the same class; both, when considered with reference to their primary origin, being equally telluric, this being understood only so far as the Earth was then regarded as a central body,* p 135 forming all things around it in the same manner was we, according to our present views, suppose the planets of our system to have originated in the expanded atmosphere of another central body, the Sun.