Page:Popular Science Monthly Volume 31.djvu/64

54 in which their components move, will for a moment adopt the belief that they have been ejected from the stars, even though he may accept the colorless theory (which explains nothing) that they were captured by the giant planets from out the star-depths.

Nor are we at all helped by remembering that the sun himself is a star, and that certain among the meteors which reach the earth may be supposed to have come from him. For assuredly the meteors regarded by Meunier and Tschermak as of terrestrial origin can not be attributed to the sun as their source, while the orbits of all the recognized meteor-streams are entirely inconsistent with such an origin. Mr. Matthew Williams, in his "Fuel of the Sun," has pictured bodies ejected from the sun which somehow come to be traveling afterward in orbits nowhere approaching within millions of miles of his surface; but no such processes are within the range of dynamical possibilities.

How, then, are we to retain at the same time what we regard as proved by Daubrée, and also those facts, inconsistent with Daubrée's theory as actually presented, which have been shown with equal certainty, either in their positive aspect (as in the case of the November and August meteor-streams) or negatively, to be certainly inconsistent with the supposed origin of meteorites from the stars? Clearly we must widen our range of survey so as to recognize an origin for meteors and meteorites which, while including Daubrée's facts, shall not exclude the others; and I think there can be very little doubt how such widening of the range of survey should be effected. Widening our survey of space will be of no service, for we only bring in more distant regions, and the meteors we have to explain require a nearer origin; but if we widen our survey of time, as assuredly we are justified in doing (for many meteorites must be millions, nay, tens, hundreds of millions of years old), we shall find other stars than those considered in Daubrée's theory, and some of these may meet our difficulty.

If there is one fact about the past of our earth and the other members of the solar system which may be regarded as certain (amid all our uncertainties in regard to the possible nebular origin of the system, or its possible origin by aggregation, or by a combination of both processes), it is that each planet began its career in a state of intense heat. I suppose no one doubts now that the giant planets retain much more of their primeval heat than the earth or Venus or Mars; nor, on the other hand, can it be reasonably doubted that the moon has parted with much more of her original heat than our earth, insomuch that, whereas, once she was the scene of such activities as we recognize in our world, she is now a cold and lifeless orb. It is in their aspect as records of the past of the planets that I note these facts. They indicate a progressive loss of heat which we only have to trace back to recognize each one of the planets, in the earliest stages of its career, as a sun-like body.

Extending, then, thus our survey in time, we find another set of