SEDIMENTARY DEPOSITS. 



which they were tranquilly buried by the matter deposited upon 

 them. Numerous remains of Crustacea and mollusca are thus 

 found in perfect preservation in strata situate at great distances 

 from the shores of the sea, figs. 3, 4. 

 Ficr. 3. 



These phenomena will be more fully explained hereafter. 



32. These circumstances establish a marked distinction between 

 the igneous and the superincumbent rocks. The latter, con- 

 sisting of matter distributed in regular and horizontal layers 

 are called STBATIFIED ROCKS, while the former consisting of 

 materials agglomerated without any semblance of order are called 



UNSTRATIFIED BOCKS. 



As the unstratified rocks are called PLUTONIC or IGNEOUS 

 HOCKS, the stratified are denominated NEPTUNIAN or SEDI- 

 MENTARY ROCKS, and sometimes ROCKS OF AQUEOUS ORIGIN. 



33. The transition or metamorphic rocks, which rest upon the 

 igneous rocks, show traces of stratification combined with such 

 partial crystallisation as may be inferred to have arisen from 

 their contact with the highly heated surface of the rocks below 

 them. The principal rocks composing the transition-system, are 

 the gneiss, already described, crystallised limestone, quartz, 

 hornblend, thick layers of the rock called the old-red sandstone, 

 and many varieties of slate and shale. 



34. Independent of the existence of distinct stratification in 

 these, they are still more decidedly distinguished from those of 

 igneous origin by the deposits of animal remains found in them, 

 which, though neither numerous nor of a high order of organisa- 

 tion, are nevertheless present in sufficient quantity to put aside 

 in the most conclusive manner all other suppositions, than that of 

 sedimentary formation and aqueous origin. 



3. It has been assumed by many geologists, that although 



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