50 ORIGIN AND NATURE OF LIFE 



the alpha-particle impinges on solid matter 

 it penetrates some way, loses its electrical 

 charge, and slowly diffuses out again as an 

 atom of helium, one of the chemical elements 

 discovered in recent years. 



This helium is the lightest member of the 

 group of inactive gases, of which the first 

 member was discovered as a natural con- 

 stituent of the atmosphere by Ramsay and 

 Lord Rayleigh, and named argon. Several 

 other members of the group were later 

 discovered, by Ramsay and his co-workers, 

 and helium is probably the most interesting 

 of the group from the circumstances of its 

 discovery and its proven relationship to 

 inorganic evolution. These elements are all 

 very inert gases which have not yet been found 

 in chemical union with each other or with 

 any other bodies. So inert are they chemically 

 that their atoms do not even unite in pairs 

 with one another to form those dual atoms, 

 or molecules, which are nearly always the 

 characteristic form in which chemical elements 

 higher in the scale of evolution unite when 

 obtained in the free elemental form by chemi- 

 cal manipulation. When chemical science 

 does succeed in uniting the members of this 

 series amongst themselves, or causes them to 

 reduplicate, it will probably be found that 



