RADIOACTIVITY. 123 



as in the rainbow, but -which in the spectral apparatus are shown as 

 a smaller or larger number of luminous lines characteristic of the 

 element in question, and separated by dark spaces between. These 

 lines have been divided into series, which show us that the light 

 emitted by an atom consists of a number of separate vibrations, which 

 may not, after the analogy of acoustic phenomena, be regarded as 

 the fundamental tone and the overtone of a vibrating body, but show 

 that the atom must consist of a larger number of minute bodies, 

 themselves vibratory. 



In the sun, where the temperature is about twice as high as the 

 most intense heat in our power to produce, the number of elements is 

 smaller than on the earth. In the stars, whose temperature, like that 

 of Sirius, for example, is higher than that of the sun, the number of 

 the elements is still smaller. Is it not reasonable, then, to suppose 

 that the number of elements in a heavenly body depends on its tem- 

 i:)erature and that through heat the complex elements are subdivided 

 into simpler ones? Yes; and if I could only accomplish that through 

 experiment, but it is again beyond my power. All these and many 

 similar phenomena indicate a possible disintegration of the elements, 

 but they do not avail to produce the experimental proof. However, 

 such a thing has now become possible. " Bodies which are smaller 

 than the atom " have been found by an exhaustive investigation of 

 the cathode rays, to which the most distinguished physicists of every 

 country have devoted their science and skill, J. J. Thomson, of Cam- 

 bridge, standing in the first rank among them. 



We speak of the cathode rays, now so often mentioned, as of a 

 stream, like water, for, as before stated, the}^ consist of a current of 

 the most minute particles, carrying a charge of negative electricity 

 and moving with the greatest swiftness. But how explain the fact 

 that these rays, these particles, can go through solid bodies without 

 harming them? Such a thing would be impossible unless the par- 

 ticles are so minute that substances as impenetrable as wood, or metal 

 even, would be to them like a coarse sieve. 



At the first glance it seems against nature that anything should 

 jDass through iron and steel plates, until we remember that it is only 

 a question of relative size. The elephant needs a door at least 2 

 meters high and 2 wide, and then perhaps goes through this great 

 opening less easily than most bacteria through the million times 

 smaller meshes of the finest hair sieve. Wliy not, then, picture to 

 ourselves forms which are a million times smaller than the smallest 

 bacteria ? It is only the question whether or not we can prove that 

 such really exist. We have thus, you see, to demonstrate the dimen- 

 sions of a cathode ray particle. Direct measurement in this case 

 is still less possible than the measurement of an atom. How- 

 ever, through the ingenious combination of the results of several 



