FOSSIL MAMMALIA. O 



these primitive masses experienced changes and convulsions 

 even previously to the appearance of life on this globe is evi- 

 dent. These masses indicate violent removals of position, some 

 of which must have taken place before they were covered by 

 the strata of shells. The disruptions we observe among them 

 are sufficient proof of this. But since the formation of the 

 secondary strata those same primitive masses have undergone 

 similar convulsions. They have, not improbably, caused, most 

 certainly they have shared in, the violent changes which have 

 as evidently taken place in the secondary strata. How, if it 

 were otherwise, could it happen that we find immense portions 

 of those primitive rocks uncovered, though not situated so high 

 as the secondary strata ? We find numerous blocks of granite, 

 &c. scattered over the secondary strata, even in situations 

 where deep valUes, where portions of the sea intervene between 

 them and those mountainous ridges from which they must have 

 been transported. They must have been driven thither by 

 tremendous eruptions or violent inundations, far exceeding in 

 force and velocity any impelling cause with which we are now 

 acquainted capable of changing the face of nature. 



To enter very deeply into an examination of the acting 

 causes which contribute at present, and have contributed ever 

 since the era at which authentic history dates its commence- 

 ment, to change the earth's surface, would be foreign to our 

 present purpose. It will be sufficient to remark that these 

 causes are rains and thaws, which bring down portions of 

 mountains ; streams which carry these on, and form what are 

 termed alluvial depositions, in places where then- course is 

 slackened ; the sea, which gradually changes the outline of the 

 land, by undermining the more elevated coasts and forming 

 precipitous clifTs, and throwing in heaps of sand upon the 

 more level shores, thus gradually overspreading a considerable 

 extent of terra firma ; and finally, volcanoes, piercing through 

 the solid strata and throwing heaps of matter around them to 

 certain degrees of extent and elevation. 



