Marine Salt. 



343 



in small boilers heated by wood. The saline mass thus 

 obtained is placed in baskets, which are suspended over 

 the boilers during the subsequent concentration. The salt, 

 moistened by the aqueous vapour, gives up almost all 

 its deliquescent salts. It is then stored, and only sent 

 into commerce after some months' keeping. During this 

 time it loses a further 28 or 30 per cent, of its weight. 

 The salt obtained by this method is very white, and fine 

 like snow. It passes under the name of igniferous salt* 



In certain cold countries, especially in Siberia, where 

 the rigour of the climate does not allow the practice of 

 salt marshes to be carried on, recourse is had to freezing 

 for obtaining salt. This process rests on the property 

 which water, saturated with salt, possesses of passing into 

 the solid state at a much lower degree than pure water. 

 If sea water is exposed to an atmosphere some degrees 

 below zero, it separates into two parts — one solid, which is 

 the water pure or nearly so ; the other liquid, which is the 

 water more or less charged. By removing the ice flakes 

 and repeating this operation several times, a liquor is 

 obtained more or less concentrated, from which it is easy 

 to obtain the salt by means of evaporation ; but this salt is 

 always very impure. 



The total production of salt in the world it is quite 

 impossible to estimate, because it is not solely an industrial 

 manufacture ; but in many localities, and especially in hot 

 countries, it is found natural and spontaneous. However, 

 it is generally believed that in Europe alone the produce is 

 about 3,000,000 tons. In France the mean average pro- 

 duction is set down at about 650,000 tons, divided as 

 follows : — Salines of the south, 300,000 tons ; salines of the 

 west, 250,000 tons; salines of the east and the Pyrenees, 



* Maigne's "Arts and Manufactures." Paris. 



