NATURAL HISTORY. 33 



explain the different theories of the earth, which 

 even to this day, agitate and divide the philoso- 

 phical world. 



As far as experience has taught us, the different 

 rocks, which constitute the crust of the globe, 

 may be classed in the following order, subject to 

 certain varieties in particular situations. 



The class of rocks, upon which all the others 

 rest, from being considered the most ancient and 

 the least subject to destruction, has been deno- 

 minated the primitive rocks. It consists of gra- 

 nite, gneis, mica slate, hornblende, syenite, por- 

 phyry, serpentine, and real marble or primitive 

 limestone. The texture of these is always more 

 or less chrystalline, a quality denoting a previous 

 chemical solution, uninfluenced by mechanical 

 deposition. They are mostly disposed in con- 

 formable, unbroken stratifications, each newer 

 stratum with lower level, as is the case with gneis 

 and mica slate ; while the granite beneath will 

 sometimes appear to rise up through them, en- 

 compassed in various manners by other rocks. 

 In the primitive rocks, no organic remains have 

 ever been found ; hence it is supposed they were 

 formed prior to the creation of animals and vege- 

 tables. They form the lowest part of the earth's 

 surface with which we are acquainted ; and not 

 only constitute the foundation on which the other 

 rocks rest, but in many situations pierce thrcn-gh 

 the incumbent rocks and strata, anc forrr he 



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