ROCK SALT 269 
Occurrence. Owing to its solubility Rock Salt is not 
found near the surface in moist climates. It occurs in 
great quantities in the British Isles, Germany, Poland, and 
in many other countries. As giving some idea of the 
extent of some of the deposits, it may be mentioned that 
amass of the mineral near Berlin has been bored through 
to a depth of 4,200 feet, whilst in Gallicia the accumu. 
lations have reached upwards of 4,600 feet. Rock-Salt 
has not been found in New Zealand. 
How Obtained. The deposits of Salt are worked in 
much the same way as seams of Coal. Shafts are sunk, and 
the mineral after being hewn out is hauled to the surface. 
In some parts of the world the underground workings 
ar very extensive—in these live whole communities of 
people, who are content with an occasional visit to the 
surface. 
Uses. Rock Salt is one of the most useful of mineral 
substances. From it is obtained much of the common 
Salt of commerce. The mineral after being taken from 
the mine is crushed and dissolved, when the earthy and 
insoluble portions settle to the bottom. The clear solu- 
tion is then run off into pans, and the Salt recovered by 
evaporation. 
From Rock-Salt also are obtained Hydrochloric Acid—so 
largely used in the manufacture of bleaching powder, and 
Carbonate of Soda, so useful for cooking and for cleansing 
purposes. Indirectly too, Soda used in the manufacture of 
Soap and Glass, is obtained from the same source. 
We have seen that Salt is fusible, and, moreover, when 
the fused mass is allowed to cool, it consolidates and 
hardens. These properties enable it to be used as a 
glaze for common earthenware. The surface of plates 
and dishes in ordinary use are sometimes seen to be 
covered with small cracks, and in some places to be 
