Page:Popular Science Monthly Volume 72.djvu/39

 many of the lines in the spectra of hydrogen, calcium, iron and other elements are missing when the light from very hot stars is broken up. For the inference is right at hand, as Professor Bigelow says, "that at extreme, at stellar, temperatures our elements themselves arc dissociated into simpler substances."

Further evidence against the atom resulted from Professor J. J. Thomson's studies of cathode rays, strict reasoning from his careful experiments demonstrating them to be swarms of minute particles, or corpuscles, as he called them, moving with velocities approaching that of light, and each weighing about one eight-hundredth as much as a hydrogen atom. These corpuscles are not merely ordinary atoms of smaller bulk, for they do not obey chemical laws, it having been ascertained, among other things, that the absorption of them by different substances is simply proportional to the latter's specific gravity, and quite independent of their chemical properties.

And recently the case against the atom, together with Thomson's ingenious demonstration of his corpuscles, has secured further experimental foundation, thanks chiefly to the labors of Becquerel, the Curies, and Rutherford and Soddy, on radioactive substances. These wonderful experiments, at once rapid and reliable, have shown that radioactivity consists in the throwing off of two orders of substances: first, atoms; second, rays or corpuscles of various kinds. But the remarkable fact in the situation is that while the atomic weight of the original substances, radium, thorium and uranium, is two hundred or more, the weight of the atoms thrown off is nearer one or two. That is, radium breaks up into, probably, helium, thrown off, and the residuum after the emission, which has a different atomic weight from either and is otherwise shown to be a distinct element. The dream of the alchemist has come true and elements are transmuted before our eyes. Science has achieved an unsurpassed triumph! But, as far as helping us to fortune goes, the dream might as well have remained a dream.

As a result of these discoveries, and many others similar, in general, in significance, it has come to be admitted that Dalton's atoms are very complex bodies, each made up of a large number of corpuscles, which are related to one another very much as are the members of a planetary system, though in size corpuscles are unimaginably minute, and the number of them constituting any atom is very much larger than the number of members in any planetary system with which we are acquainted.