234 GEOLOGY. 



ered by them in Russia. In this country the rocks are 

 limestones, sandstones of various colors, shales or marls, 

 gypsum beds, and conglomerates. In the Permian stra- 

 ta of Europe the limestones are mostly found to be mag- 

 nesian. Why this is so the researches of geologists have 

 as yet not been able to determine ; and Phillips remarks 

 in regard to it that " we must be content to shelter our 

 ignorance under the statement that, from some unknown 

 cause, the waters of the sea were then decomposed in 

 such a way as to permit very generally the precipitation 

 of united magnesian and calcareous carbonates." 



336. North America at the Close of this Age. Two 

 thirds of the North American Continent was above the 

 level of the ocean at the close of the Carboniferous age. 

 This was the eastern part, while the western was occu- 

 pied by a large interior or mediterranean sea, such as in 

 the Silurian and Devonian ages extended over much of 

 the eastern part also. The Rocky Mountains, as well 

 as, indeed, the Alleghanies, did not yet exist. The bor- 

 ders or fringes of the continent on the south and east 

 were yet to be added, and also a large portion of the 

 western part of the continent. Florida, that great work 

 of the coral animals, was yet to be constructed. Al- 

 though so much was done, long ages upon ages were yet 

 to be passed before the continent would be completed. 



337. Disturbances in the Coal-measures. The strata 

 of the Carboniferous age have been subjected to upheav- 

 als, foldings, fractures, etc., like all other strata, some of 

 them being very extensive, even mountainous. If it were 

 not for these, few of the beds of coal lying between the 

 thousands ( 318) of feet of strata would have come with- 

 in the reach of man in his minings. Most of these up- 

 heavals and flexures occurred at the close of the age, in 

 the interval between Palaeozoic and Mesozoic time. The 

 results are so observable in this country, all along the re- 

 gion of the Appalachian chain, that the change produced 

 at that time has been called the Appalachian revolution. 



