118 ItOM* CROPS FEED. 



clay into granite. These rocks, which are the result of 

 the united action of heat and water, are termed meta- 

 morphlc (i. e,, metamorphosed) rocks. 



One of the most obvious division of rocks is into Crys- 

 talline nnd Fragmentdl. 



Crystalline Rocks are those whose constituents crystal- 

 lized at the time the rock was formed. Here belong both 

 the igneous and metamorphic rocks. These are often 

 plainly crystalline to the eye, i. e., are composed of re.idily 

 perceptible crystals or crystalline grains, like statuary 

 marble or granite; biit they are also frequently made up 

 of crystals so minute, that the latter are only to be recog- 

 nized by tracing them into their coarser varieties (basalt 

 and trap.) 



Fra^mental Rocks are the sedimentary rocks, formed 

 by the cementing of the fragments of other older rocks 

 existing as mud, sand, etc. 



The Crystalline Rocks may be divided into two 

 great classes, viz., the slUchus and calcareous ; the first 

 class containing silica, the latter, lime, as the predomina- 

 ting ingredient. 



The silicious rocks fall into three parallel series, which 

 have close relations to each other. 1. The Granitic series ; 

 2, The Syenitic series; 3. The Talcose or Magnesian 

 series. In all the silicious rocks quartz or feldspar is a 

 prominent ingredient, and in most cases these two minerals 

 are associated together. To the above are added, in the 

 granitic series, mica ; in the syenitic scries, amphihole or. 

 pyroxene ; and in the talcose series, talc^ chlorite^ or ser- 

 pentine. The proportions of these minerals vary indef- 

 initely. 



The Granitic Series 

 consisting principally of Quartz^ Feldspar, and Mica. 



Granite. — A hard, massive* rock, either finely or 



• Rocks are massive when they have no tendency to split ii.to slabs or plates 



