Rock Salt and Gypsum. Granites. 6 1 5 



low in the series, and, as already explained, was the 

 result of the solar evaporation of an inland lake, 

 like, for example, the great salt lake near Utah, in the 

 Eocky Mountains, or of the salt lakes of central 

 Asia. The waters that ran into it contained quantities 

 of salt in solution ; and as the lake had no outlet, and 

 only got rid of its water by evaporation, concentration 

 of the chloride of sodium ensued, till at length super- 

 saturation being induced, precipitation of rock-salt 

 took place. The same formation yields the greater part 

 of the gypsum quarried in England, though some also 

 occurs in the Red Marl of the Magnesian Limestone 

 series. 1 



In Devonshire and Cornwall, on Shap Fell in West- 

 moreland, and in Scotland chiefly near Aberdeen, the 

 granite quarries afford much occupation to a number 

 of people. Now that it has become the fashion to 

 polish granites, these rocks are becoming of still more 

 importance. But as they are not so easily hewn as 

 sandstone, they do not come into use as ordinary 

 building stones, except in such districts as Aberdeen, 

 where no other good kind of rock is to be had. 

 Basalt, Greenstones, and Felspathic porphyries from 

 North Wales, Scotland, Charnwood Forest, and other 

 districts in England, are also largely employed for 

 building and road-making, and the Serpentines of 

 Cornwall and Anglesea, and the Marbles of the Car- 

 boniferous Limestone of Derbyshire, yield beautiful 

 materials for ornamental purposes. 



I have now attempted to give an idea of the general 

 physical geography of our country, both in ancient and 



1 For a full account of the physical formation of these deposit s > 

 see ' Journ. Geol. Soc.' 1871, vol. xxvii, pp. 189 and 241. Ramsay. 



