EXPLORING THE ATOM 



tial thing in the universe, and that what we are 

 accustomed to think of as the absolutely immaterial 

 ether is in truth a structure of enormous density. 

 ,Yet this conclusion is arrived at along different lines 

 of reasoning, and it is one upon which the most 

 authoritative physicists are agreed. 



Thus Sir J. J. Thomson assures us that the unit 

 particle of electricity, called a corpuscle or electron, 

 owes its mass entirely to an infinitesimal quantity of 

 ether which is in some way bound up with its sub- 

 stance; and as all matter, in his view, is supposed to 

 be built up of electrons, it follows that "all mass is 

 mass of the ether, all momentum momentum of the 

 ether, and all kinetic energy kinetic energy of the 

 ether." Professor Thomson then goes on to assure 

 us that "since we know the volume of the corpuscle 

 as well as the mass, we can calculate the density of 

 the ether attached to the corpuscle ; doing so we find 

 it amounts to the prodigious value of about 2,000,- 

 000,000 times that of lead." He adds, however, that 

 this would be the density of the ether only in the 

 immediate vicinity of the electron or corpuscle and 

 that its density elsewhere in space would be consider- 

 ably less, if the ether is compressible. 



To make somewhat comprehensible the paradox 

 that matter as we know it is able to move freely in 

 a medium of such density, Sir Joseph Thomson gives 

 us this illustration: "Although at first sight the idea 

 that we are immersed in a medium almost infinitely 

 denser than lead might seem inconceivable, it is not 

 so if we remember that in all probability matter is 

 composed mainly of holes. We may in fact regard 



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