i [6 THE STORY OF THE EARTH, 



sometimes breccia derived from the Carboniferous 

 limestone. The middle portion is a great wedge of 

 magnesian limestone, resting upon the marl slate, 

 600 feet thick in the east of England, and 10 or 

 20 feet in the west. The upper sandstones and 



. > with gypsum, like the lower beds, are thick 

 in the west and thin in the east: but are only 

 about one-fifth of the thickness of the lower 

 sandstone. The lower 3000 feet of variegated 

 Istone is identified with the German rothlie- 

 gende. The marl slate is identified with the 

 kupferschiefer, and the zechstein with the mag- 

 nesian limestone. The lower Uunter of Germany 

 has been compared with the gypseous marls of the 

 Eden basin in Cumberland. 



The magnesian limestone probably was origi- 

 nally an ordinary limestone formed of calcite, and 

 the carbonate of magnesia was apparently infil- 

 trated into it. There is no more singular deposit 



anywhere to be seen than the exposure oi this 

 rock at Sunderland, where some of the beds now 



sist of radiating concretions of globular form 

 and variable size, giving the rock an appearance 

 of being built of shot or cannon-balls. 



The Permian age was a tune of considerable 



volcanic activity, and intei'stratified beds of vol- 

 canic ash and lava are well seen in the country 

 about Exeter, and in Ayrshire, as well as in 



many. 



In other parts of the world the Permian forma- 

 tion attains a great development in thickness, and 



contains important beds of coal. The Gondwana 



rocks of India, whi< h are -probably Comparable to 



the Permian of Russia, \< ry 1 losely resemble the 



•man rocks of the Karoo m South Africa, both 



al, and the flora is probably Permian, 



