"This entire ex-terrestrial fauna hitherto discovered, which already comprises about fifty different species, and which originates from different meteoric falls, even from some during the last century, conveys the impression that it doubtlessly once formed part of _a single ex-terrestrial-celestial body_ with a unique creation, which in by-gone ages seems to have been overtaken by a grand catastrophe, during which it was broken up into fragments."[1] When we remember that meteors are now generally believed to be the droppings of comets, we come very near to proof of the supposition that comets are the _débris_ of exploded planets; for only on planets can we suppose that life existed, for there was required, for the growth of these sponges, corals, and crinoids, rocks, earth, water, seas or lakes, atmosphere, sunshine, and a range of temperature between the degree of cold where life is frozen up and the degree of heat in which it is burned up: hence, these meteors must be fragments of bodies possessing earth-like conditions. We know that the heavenly bodies are formed of the same materials as our globe. Dana says: "Meteoric stones exemplify the same chemical and crystallographic laws as the rocks of the earth, and have afforded no new element or principle of any kind."[2] It may be presumed, therefore, that the granite crust of the exploded globe from which some comet was created was the source of the finely triturated material which we know as clay. But the clays are of different colors--white, yellow, red, and blue. [1. "Popular Science Monthly," November, 1881, p. 86. 2. "Manual of Geology," p. 3.] {p. 75} "The aluminous minerals contained in granite rocks are feldspar, mica, and hornblende. . . . Mica and hornblende generally contain considerable oxide of iron, while feldspar usually yields only a trace or none. Therefore clays which are derived from feldspar are light-colored or white, while those partially made up of decomposed mica or hornblende are dark, either bluish or red."[1] The tail of the comet seems to be perpetually in motion. It is, says one writer, "continually _changing and fluctuating_ as vaporous masses of cloud-like structure might be conceived to do, and in some instances there has been a strong appearance even of an _undulating movement_."[2] The great comet of 1858, Donati's comet, which many now living will well remember, and which was of such size that when its head was near our horizon the extremity of the tail reached nearly to the zenith, illustrated this continual movement of the material of the tail; that appendage shrank and enlarged millions of miles in length. Mr. Lockyer believed that he saw in Coggia's comet the evidences of a _whirling_ motion-- "In which the regions of greatest brightness were caused by the different coils _cutting_, or appearing to cut, each other, and so in these parts leading to compression or condensation, and _frequent collision of the luminous particles_."