101 



GENERAL CONSIDERATIONS 



KESPECTING THE 



OEIGIN OF THE ANIMATED TEIBES, 



THUS concludes the wondrous section of the earth's history 

 which is told by geology. It takes up our globe at an early 

 stage in the formation of its crust ; conducts it through what 

 we have every reason to believe were vast spaces of time, in 

 the course of which many superficial changes took place, and 

 vegetable and animal life was gradually evolved ; and drops it 

 just at the point when man was apparently about to enter 

 [or had just entered] on the scene. The compilation of such 

 a history, from materials of so extraordinary a character, and 

 the powerful nature of the evidence which these materials 

 afford, are calculated to excite our admiration, and the result 

 must be allowed to exalt the dignity of science, as a product 

 of man's industry and his reason. 



It is now to be remarked, that there is nothing in the 

 whole series of operations displayed in inorganic geology 

 which may not be accounted for by the agency of the ordinary 

 forces of nature. Those movements of subterranean force 

 which thrust up mountain ranges and upheaved continents, 

 stand in inextricable connexion, on the one hand, with the 

 volcanoes which are yet belching forth lavas and shaking large 

 tracts of ground, as, on the other, with the primitive incan- 

 descent state of the earth. Those forces which disintegrated 

 the early rocks, and of the detritus formed new beds at the 

 bottom of seas, are still seen at work to the same effect in 

 every part of the globe. To bring these truths the more 

 clearly before us, it is possible to make a substance resembling 

 basalt in a furnace ; limestone and sandstone have both been 

 formed from suitable materials in appropriate receptacles ; the 



