NATURAL HISTORY. 37 



some peculiar to the country in which they are 

 found, some only to be met with in the living 

 state in distant parts of the world and under a 

 very opposite climate, and others in which the 

 species is altogether extinct. 



It is these alluvial deposits which supply us 

 with some of the principal materials for our build- 

 ings, for the formation of our roads, and for 

 many of our useful manufactures, and which fur- 

 nish the requisite papulum from which vegetation 

 in general derives its support and growth ; and it 

 is from these deposits that gold and many of the 

 precious stones are extracted. 



Thus the crust of the earth, which encircles 

 the globe, as far as man has been able to pene- 

 trate, is made up of four formations, supposed to 

 have been effected at different periods and under 

 different circumstances ; each containing mate* 

 rials highly useful, and affording a noble scope for 

 the investigation of the philosopher. These mate- 

 rials, the situation of which can only be acquired 

 by a knowledge of geology, present most incon- 

 testible proofs of a previous order of things, which 

 has been perverted by some great revolution or 

 convulsion, that alone can account for the very 

 extraordinary appearances which are so frequent- 

 ly to be met with upon examining the contents of 

 the earth. And whether these phenomena have 

 been produced by the agency of fire according to 

 the doctrine of one set of philosophers, or by 



