﻿400 Sir W. Ramsay and Dr. Spencer on Ckemical and 



is of the nature of surface tension. Here the analogy fails ; 

 for the reason that electric corpuscles accumulate on the surface 

 and not in the interior, is probably due to the repulsion of 

 the corpuscles for each other. Yet, as it is advisable to make 

 some kind of mental picture, this imperfect analogy must 

 serve. And it may be conceived that the long-known process 

 of electrification by friction may consist in the rubbing off 

 or the rubbing on of electrons. We are accustomed to speak 

 of the " electrification of a rod of sealing-wax. " In this case 

 it may be supposed that the surface layer of the sealing-wax 

 acquires electrons (i. e. a negative charge) from the wool or 

 fur with which it is rubbed. When glass is rubbed with 

 silk, on the other hand, the process may be viewed as the 

 removal of electrons from the surface of the glass by friction 

 with a silk cloth. These actions relate mainly, if not wholly, 

 to the surface layer ; but it is not impossible that ionic charges 

 may be influenced in a minor degree. 



Lastly, it is' not merely conceivable, but highly probable, 

 that the atom of a metal may lose not only its " metallic 

 corpuscle " (i. e. the corpuscle the loss of which changes it to 

 an ion) but also other electrons. It is true that only in one 

 single instance has this been certainly proved. Ramsay and 

 Collie investigated the spectrum of the gas (emanation) 

 evolved continuously from salts of radium, and found it to 

 be definite and characteristic. Its volume was measured by 

 Ramsay and Soddy, and it was found to be a gas, resembling 

 other gases in conforming with Boyle's law ; it was investi- 

 gated originally by Rutherford and Soddy, who showed that 

 like other gases it can be solidified by cold. They also showed 

 that it is certainly an elementary gas, very like the gases of the 

 argon group, for it is unaffected by treatment with any re- 

 agent. When freshly prepared its spectrum shows no trace 

 of the very characteristic lines of helium. Yet Ramsay and 

 Soddy showed that when kept it changes largely into helium 

 indubitably recognizable by its spectrum. The volume of 

 helium produced was measured and amounts to between 

 three and four times that of the emanation. At the same 

 time the Curies and Rutherford have shown that this spon- 

 taneous change is attended by the loss of relatively enormous 

 amounts of energy, and that during the change j3 rays, or 

 electrons, are shot off from it with enormous velocity. Such 

 electrons are characterized by their ability to pass through 

 screens impermeable to molecules of " ordinary matter/' 

 Elster and Geitel and others have proved that similar cor- 

 puscles are shot off from many forms of ordinary matter ; 

 and it is only reasonable to draw the conclusion that the 



