BEF06ITES. 



15 



GEOLOGICAL DEPOSITES. 



The earth is composed of masses of rocks and detritus, Regular 

 which are more or less extensive and uniform in their charac- ^I^'? f T*"' 

 teristic constituents. At least such is the exterior structure i^es. 

 of the earth, from its outer surface to the greatest depths to 

 which it has been laid open for inspection. These masses are 

 mostly in regular deposites ; and those of the same structure 

 and composition regard the same order of superposition in 

 relation to each other. A few of the outermost masses are in- 

 dependent anomalous deposites^ having no reference to each 

 other. 



As those deposites which are geologically the lowest are pj^j^jitiyg 

 mostly highly elevated, and more universal than the superim- rocks the 

 posed ones, and always form the most prominent superficial point. ^ 

 starting points, we begin with them in a geological nomencla- 

 ture, . 



REGULAR DEPOSITES, 



Are distributed into five Series, called Classes. Each se- Five series, 

 ries consists of three formations, which formations are found Three for- 

 te be corresponding equivalents in all the series. The lowest 

 formation in each series is slaty or argillaceous, and always 

 contains beds of carbon in the state of coal, anthracite, or 

 plumbago. The next is silicious, and destitute of beds of car- 

 bon. The uppermost is chiefly cai'bonate of lime, also desti- 

 tute of beds of carbon. But each formation embraces beds, 

 alternating layers, veins, and disseminations of mineral bod- 

 ies, often of great extent, which are not essential constituents 

 of it. In some cases, however, they are so abundant and so 

 striking in their characters, that they give names to general 

 strata ; as metalliferous, ferriferous, saliferous, &c. 



