THE BEGINNINGS OF LIFE. 101 



have high atomic weights, whilst others, such as so- 

 dium and potassium, the atomic weights of which are 

 low, are much less changeable. In binary compounds 

 of these several metals having high atomic weights 

 there would be a greater difference between the weights 

 of the component elements, than if we had to do with 

 compounds of the small-atomed metals, and so also, 

 it has been found that it is precisely those compounds 

 which consist of the most dissimilar elements that are 

 the most decomposable. But there is also another 

 most interesting aspect of the question. Mr. Spencer 

 says : c Strong confirmation of this view may be drawn 

 from the decomposing actions of those longer ethereal 

 waves which we perceive as heat. On contemplating 

 the whole series of binary compounds, we see that the 

 elements which are most remote in their atomic 

 weights, as hydrogen and the noble metals, will not 

 combine at all : their vibrations are so unlike that they 

 cannot keep together under any conditions of tempe- 

 rature. If again we look at a smaller group, as the 

 metallic oxides, we see that whereas those metals that 

 have atoms nearest in weight to the atoms of oxygen, 

 cannot be separated from oxygen by heat, even when 

 it is joined by a powerful collateral affinity; those 

 metals which differ more widely from oxygen in their 

 atomic weights, can be de-oxidized by carbon at high 

 temperatures ; and those which differ from it most 

 widely, combine with it very reluctantly, and yield 

 it up if exposed to thermal undulations of moderate 



