588 MANUAL OF NATURAL HISTORY. 



springs, as those of Sweden, deposit sesqui-oxide of 

 iron, which is called bog or marsh iron, and, mixed 

 with sand or gravel, forms sand-ore. In many 

 springs, as in those of Vienna, gypsum and chloride 

 of calcium are thrown down ; several lakes of Russia 

 also deposit a saline crust ; and in Egypt, soda is 

 likewise deposited. The turf-moors at Frauzenbad 

 are coated with sulphate of soda, or " Glauber-salt/' 

 and sulphate of iron ; and the limestone caverns of 

 Brazil and Ceylon are incrusted with nitrate of po- 

 tassa, or saltpetre. In the neighbourhood of the 

 Dead-Sea, and in the island of Trinidad, there are 

 springs of mineral-oil, which, on drying, become 

 Asphalt. 



Rivers, in passing through rocks rich in ores, often 

 separate particles of these precious substances from 

 their matrix, which are afterwards deposited or 

 thrown down : as shewn in the stream-gold, tin, 

 platinum, and magnetic-iron, found in Wicklow, the 

 Ural Mountains, Brazil, Australia, and California. 

 All platinum, and the greater portion of gold, is pro- 

 cured in this manner; as are likewise the gold of 

 Borneo, the zircon of Bohemia, the hyacinths and 

 chrysoberyls of Ceylon, and the diamonds of Brazil. 



Turf consists of moss, marsh, and water plants, 

 which have gradually died and become changed into 

 a brown, combustible substance ; turf-formations 

 are extensive in Ireland, where they constitute the 

 great bogs ; and in Hanover, and at San Paulo, in 

 the Brazils, they are likewise developed on a large 

 scale ; a kind of turf is formed on the shores of the 



