FORMATIONS AND PHYSICAL HISTORY 



473 



may be doubted, however, whether there is a salt layer of this 

 thickness. Besides common salt, salts of potash and magnesium 

 are present locally in such quantity as to be commercially val- 

 uable. With the exception of saltpetre, the world's supply comes 

 from these beds. 



The system underlies the larger part of Russia (in Europe), and 

 appears at the surface over a large area in the southeastern part of 



. 405. Sketch map of Europe during the later part of the Permian period. 

 c lines indicate areas of marine deposition, the broken lines areas of lagoon de- 

 its. (After De Lapparent.) 



that country. Here and in southern Europe generally the Permian 

 is conformable on the Carboniferous, and is partly marine and 

 partly non-marine. In Russia it contains salt, gypsum, etc., and 

 also, at some horizons, marine fossils. 



Other continents. In other parts of the world the Permian is 

 widely developed. In countries about the Indian Ocean, there is 

 a less distinct break between the Carboniferous and Triassic systems 

 than in Europe, and locally at least, the Permian seems to bridge 

 the interval completely. 



