GEOLOGY. 493 



of which the crust of the earth is composed into Primitive and 

 Secondary ; the first including rocks destitute of fossil organic 

 remains, and which he considered as disposed in highly inclin- 

 ed strata, and forming the most lofty points on the earth's sur- 

 face ; the second comprehending rocks containing petrifactions, 

 or associated with others including such remains, disposed in a 

 form more horizontal, and forming the lower and softer portions 

 of the land surface. Werner pointed out another class of 

 rocks which he named Transition, from exhibiting the blended 

 characters which show the transition of the primitive to those 

 of a secondary description. The same naturalist formed a 

 fourth class of rocks under the term Mluvial, as designating 

 these more loosely compacted masses of clay, marl, loam, &c. 

 which rest on the more solid and older rocks ; and he termed 

 a fifth class of mineral masses, formed by the agency of subter- 

 raneous fire, Volcanic rocks. 



I. PRIMITIVE ROCKS. Primitive Rocks are distinguished 

 by the absence of all fossil organic remains ; and it has hence 

 been inferred, that there was a period in the history of our pla- 

 net when plants and animals did not exist. The rocks of this 

 class lie under those of the succeeding classes, and frequently 

 also rise through them to a great height, in the form of mountains 

 and mountain chains. Countries composed of primitive rocks are 

 generally more rugged and lofty, their inequalities more con- 

 spicuous, and their vallies deeper, narrower, and more uneven 

 than in districts composed of secondary rocks. The strata of 

 primitive mountains are also remarked as being also higher in- 

 clined than the secondary class ; and in many countries pre- 

 serve a uniformity of direction. In Scotland their general di- 

 rection is from N. E. to S. W. and the same is nearly the case 

 in the alpine regions of Norway, and other mountain chains in 

 Europe. They abound in metalliferous minerals, as tin, wol- 

 fram, and molybdena. Gold, silver, lead, copper, iron, cobalt, 

 zinc, manganese, arsenic, and mercury occur either disseminat- 

 ed in beds, or veins, in various rocks of this class ; and the 

 most beautiful of all the gems occur in great variety in the pri- 

 mitive rocks. 



The rocks of the primitive series are granite, porphyry, trap, 

 serpentine, limestone, gneiss, mica-slate, clay-slate, and quartz 



