142 
CLARKE. 
gen was reached. At that point the process exhibited its 
maximum energy, and beyond it the elements forming stable 
oxides were the most rapidly developed, and in the largest 
amounts. On this supposition the scarcity of the elements 
above iron becomes somewhat intelligible; but the theory 
does not account for everything and is to be regarded as merely 
tentative. It is legitimate only so long as its purely specu¬ 
lative character is kept clearly in view. If, however, the 
evolution of the elements is admitted, it is clear that the later 
stages of the process must have been seriously conditioned 
by the chemical affinities developed at first. 
