Page:Popular Science Monthly Volume 64.djvu/485



HERE are times when the atmosphere seems to be fairly saturated with the spirit of scientific discovery. Such a time existed during the opening years of the nineteenth century when John Dalton was putting the atomic theory of matter upon an experimental rather than upon the purely speculative foundation upon which it had previously rested; when Count Rumford, an American by birth, was laying the corner-stone of the modern mechanical theory of heat, in accordance with which heat consists in the vibratory motion of the particles of which matter is composed; when Thomas Young was forging the final links in the chain of proof that light consists in the wave motion of some all-pervading medium, the ether.

It is not a little interesting that the opening years of the twentieth century have also been marked in no less a degree than those of its predecessor by epoch-making discoveries in physics. Most of this new activity has been grouped about the general subject of radiation, discoveries of new rays having followed one another in such rapid succession that it is difficult even for a physicist to keep posted about them all. As a result of these discoveries important progress has been made toward the solution of one of the most fundamental questions with which science has to deal, viz., the question as to the nature and the constitution of matter.

The discovery of X-rays is to be regarded as the starting point of this epoch of investigation upon radiation. It was in the Christmas