IX THE LAST HALF- CENTURY. 135 



and often afford convincing evidence of 

 it. At the same time, it has been shown 

 that certain forms persist with very little 

 change, from the oldest to the newest fos- 

 siliferons formations ; and thus show that 

 progressive development is a contingent, 

 and not a necessary result, of the nature 

 of living matter. 



Geology is, as it were, the biology of Geology. 

 our planet as a whole. In so far as it 

 comprises the surface configuration and 

 the inner structure of the earth, it answers 

 to morphology ; in so far as it studies 

 changes of condition and their causes, it 

 corresponds with physiology ; in so far as 

 it deals with the causes which have effect- 

 ed the progress of the earth from its ear- 

 liest to its present state, it forms part 

 of the general doctrine of evolution. An 

 interesting contrast between the geology 

 of the present day and that of half a cent- 

 ury ago, is presented by the complete 

 emancipation of the modern geologist 



