38 Iftature'a /BMracles. 



at the present day by uniting the chlorine gas 

 with common lime, forming a chloride of lime, 

 which is used for bleaching and purifying 

 purposes. 



Salt is found in great quantities as a 

 natural product under the name of rock salt. 

 It is found in some parts of the world in great 

 veins over 100 feet in thickness. In some 

 cases the rock salt is mined, when it has to be 

 purified for commercial purposes. The com- 

 mon mode of obtaining salt, however, is by 

 pumping the solution from these great beds 

 where it is mingled with water salt water; 

 the water is then evaporated, and when it 

 reaches a certain stage of evaporation the salt 

 crystallizes and falls to the bottom. 



Different substances crystallize in different 

 forms. The crystallization of water when it 

 freezes, as we shall see hereafter, arranges 

 its molecules in such a form as to make a 

 lump of ice of given dimensions lighter than 

 the same dimensions of water would be. Salt 

 in crystallizing does not follow the same law; 

 the salt crystal is in the shape of a cube and is 

 denser in its crystalline form than in solution, 

 hence it is heavier and falls to the bottom. 



It is said that there is a deposit of rock salt 

 in Galicia, Austria, covering an area of 

 10,000 square miles. There are also very 

 large deposits in England, the mining of 

 which has become a great industry. There 



