(JEOLOGICAL RELATION. 185 



tainty of a science, but it is from time to time amply 

 repaying the benefit, by making kno-\vn the condition of 

 the animal kingdom at remote periods of time. We 

 are thus enabled to obtain glimpses of the state of the 

 earth -when races of animals very different from those 

 now living inhabited it, and to note their successive ap- 

 pearances and decline, until at length we reach the time 

 when animals which are still extant began to prevail. 

 The results afforded by such observations are among the 

 most Avonderful presented to us by science. They tend 

 to enlarge our ideas of the power of the Creator, while 

 they multiply infinitely om' conceptions of the unlimited 

 variety of created things, and of the immeasurable du- 

 ration of their existence. 



Guided by the light reflected from geological sci- 

 ence, we may feel rationally authorized to draw from 

 the preceding facts and considerations the following 

 inferences. That our existing species of land moUusks 

 were Hving at a period which, though recent in a geo- 

 logical sense, was anterior to the last geological revolu- 

 tion, when the surface of this portion of the earth was 

 brought to its present condition, and to the existence of 

 the higher orders of animals which now inhabit it, and 

 even to that of the extinct mammaUans which are known 

 only by their gigantic remains. That, during the period 

 of the deposition of the newest tertiary beds they 

 were at least as numerous as at present, and that conse- 

 quently, the existing epoch cannot be considered as that 

 of their greatest development. That, in the interval of 

 VOL. I. 23 



