§45. RETROSPECT. 191 



have witnessed the effects of repeated changes in the relative 

 level of the land and water, — have seen that our present 

 plains and valleys were submerged beneath the ocean, at a 

 period when large mammalia, apparently unrestricted by 

 existing geographical limits, were inhabitants of regions 

 which are now no more ; — and we have obtained additional 

 proof that — 



New worlds are still emerging from the deep, 

 The old descending in their turn to rise ! 



Even in this early stage of our progress, we have con- 

 clusive evidence of the extinction of whole tribes of ani- 

 mals, alike admirably adapted to the conditions in which 

 they were placed, as the races which have survived. And 

 it is most gratifying to the geologist to find, that this fact, 

 which but a few years since was received with hesitation 

 by most, and condemned and rejected by many, is now 

 adduced by the moralist and divine, as affording new and 

 striking proofs of the wisdom and overruling providence 

 of the Eternal.* 



* See Dr. Buckland's Bridgwater Essay. 



