Page:Popular Science Monthly Volume 12.djvu/163

Rh Lindsay's opinion, which is in any case a somewhat bold inference from a single observation. Assuredly the discovery just made is in direct opposition to a certain argument, derived from the gaseity of nebulæ, in favor of the gaseous hypothesis of Laplace—an argument which had always appeared to the present writer insufficiently established. But the nebular hypothesis, regarded not merely in the form suggested by Laplace (in which form it was utterly inconsistent with physical facts now known), but in the wider sense which would simply present our solar system in the remote past as in a nebular state, without defining its nebulosity as due either to gaseity on the one hand, or to a mixed meteoric and cometic constitution on the other, has most certainly not received a shock, but rather receives strong support, from Mr. Copeland's observation. A theory of the evolution of the solar system, advocated by me during the last seven years, according to which the solar system had its origin in meteoric and cometic aggregation, requires that during the long ages through which the process of development continued there should be occasional outbursts of light and heat in moderate degree from the rest of the system, even to its outskirts. That intense heat imagined by Laplace as pervading the entire gaseous mass, extending originally far beyond the path of the remotest planet of our system, would require, indeed (if it were a physical possibility in other ways), that the spectrum of a developing solar system should be uniformly that of gaseity for millions on millions of years. If it had been found or could be proved that the gaseous nebulæ are in a state of intense heat, Laplace's gaseous hypothesis would have had one powerful argument in its favor. This argument has been strongly urged by those who have taken that special view of the gaseous nebulæ which the recent discovery shows to be erroneous. But those who have maintained, as I have, that in the gaseous nebulæ we probably "see vast systems of comets traveling in extensive orbits around nuclear stars," will find confirmation, not disproof, in the discovery lately made, especially when considered in combination with the circumstance that Prof. Wright, of Yale, has found the cometic spectrum to be emitted by meteoric masses exposed to moderate heat; while, under slight changes of condition, the cometic spectrum of bright carbon bands appears to give place to the nebular bright-line spectrum.

However, speculation apart, we have in the discovery just made a most important fact for our guidance—the fact, namely, that a body which to ordinary observation has been in all respects like the star in the Crown, and even under spectroscopic observation shone for a while with true stellar light, has dwindled into a nebula giving the spectrum which has heretofore been regarded as indicative of ordinary gaseity.—English Mechanic.