124 RADIOACTIVITY. 



researches, we are able to compare mathematically the size of such 

 paiticles with the; size of an atom. 



I lijive already referred to the fact tliat the cathode rays carry a 

 negative; electric chai'<>-e, and it has been demonstrated that each 

 particle contains a so-called elementary quantity of electricity, or the 

 amount that an atom of hydrogen carries through the galvanic 

 stream at the decomposition of water. We should therefore think 

 it reasonable if such a particle were of the same size as the hydrogen 

 atom. On the contrary, the astonishing fact appears that the size 

 of a cathode-ray particle is at least one thousand times less than that 

 of the hydrogen atom, the smallest of all hitherto known atoms; 

 that is, a thousand times smaller than the body, which, as the name 

 implies, is so minute as to have been heretofore considered indivisible. 

 This recently discovered particle carrying an elementary quantity of 

 negative electricity has been named an electron. 



It will be readily believed that physicists would not accept a state- 

 ment so contradictory to the views previously held without rigid 

 examination, and that the existence of the electron would not be 

 credited without further proof. But since numerous investigators, 

 working by different methods, have found the same value for the mass 

 of the unknown electron, and after this value has proved itself 

 invariable, whether the electrons were produced by an electric dis- 

 charge through a vacuvnn tube, or by an illumination with ultra- 

 violet or X-rays, or by means of a Bunsen burner or a thorium 

 preparation, and, further, after it has been shown that it is entirely 

 indifferent which gas we work in, whether hydrogen, oxygen, or the 

 air, we can not deny the fact that a negative electron of a mass 

 approximately one one-thousandth of that of the hydrogen atom can 

 be isolated from every substance. 



The question at once arises, have we here th<> piimal sul)stance in- 

 forming all matter and out of which the entire universe is built up? 

 Is the electron the already long sought for primary atom, through the 

 grouping of which in varying numbers and diverse positions all 

 material substances, and consequently the primary elements them- 

 selves, oi'iginate? May we not hope that the chemical structure of 

 the atom depends on the chemical structure of the molecule? Since 

 each chemical atom is characterized by its own spectrum, may not 

 one imagine that each atom illustrates in an infinitesimal degree a 

 ])lanetai'y system, in which the central body would be a positively 

 electrified germ around wliich, according to the element under obser- 

 vation, a differing number of electrons perform their revolutions in 

 prescribed jiaths, exactly as the eai'th, Mercury, Jupiter, Saturn, and 

 the rest continue their endless circuits around the sun ? Many physi- 

 cists believe this to be so, but it is still too early, would lead too far, 

 and as yet we know too little about the electron to attempt to decide 



