112 AQUEOUS EOCKS 



is an almost universal constituent of terrestrial waters, though 

 often in but the merest traces. Its prevailing solid form is that 

 of coarsely granular aggregates constituting the so-called roch- 

 salty the beds of which are often of such thickness and extent 

 as to constitute true rock masses and entitle them to considera- 

 tion here. These rock masses are invariably products of depo- 

 sition from solution, a deposition brought about through the 

 evaporation of saline waters in enclosed lakes or seas. They 

 are not limited to any particular geological period, but are to be 

 found wherever suitable conditions have existed for their for- 

 mation and preservation. Some of the more important beds 

 now known belong to either the Upper Silurian, Carboniferous, 

 Triassic, or Tertiary periods, and vary in thickness from a mere 

 film to upwards of 1200 feet. In the United States, beds of 

 rock-salt are known to occur in the states of New York, Penn- 

 sylvania, Ohio, Virginia, West Virginia, Michigan, Kansas, 

 Kentucky, Texas, Wyoming, California, and Nevada. Canada, 

 England, the Carpathian Mountains, the Austrian and Bavarian 

 Alps, West Germany, the Vosges, the Jura, Spain, the Pyrenees 

 and Celtiberian mountains, all contain important beds. With 

 the rock-salt are not infrequently associated other salts, as above 

 noted. In the celebrated Stassfurth deposits, sixteen different 

 compounds in the shape of chlorides and sulphates of sodium, 

 potassium, magnesium, calcium, and iron have been determined, 

 many of them in sufficient quantity to be of commercial value. 



2. EOCKS FORMED AS SEDIMENTARY DEPOSITS AND FRAG- 

 MENTAIi IN STRUCTURE: CLASTIC 



The rocks of this group differ from those just described in 

 that they are composed mainly of fragmental materials derived 

 from the breaking down of older rocks, or are but the more or 

 less consolidated accumulations of organic and inorganic debris 

 from plant and animal life. The group shows transitional 

 forms into the last, as will be illustrated by certain of the lime- 

 stones and the quartzites. They are water deposits, and, as a 

 rule, are eminently stratified or bedded, although this structure 

 is not always apparent in the hand specimen. 



As will be readily comprehended when one considers from 

 what a multitude of materials the fragmental rocks have been 

 derived, the amount of assorting, admixture with other sub- 

 stances, solution, and transportation by streams these materials 



