340 The Commercial Products of the Sea. 



on the Channel coast, 36 on the shores of the ocean, and 

 45 on the coasts of the Mediterranean. These consist of 

 one or more reservoirs, into which the sea water is passed. 

 Those of the south are greatly superior to the others, be- 

 cause they are better managed, and the climate is more 

 favourable for evaporation. 



The sea water is introduced, either by means of a canal 

 of the level of the sea banks, or by means of hydraulic 

 machines in other cases, into a reservoir, which is shallow 

 and of great extent of surface, so that the liquid may be 

 subjected to the action of the sun's rays. In this reservoir, 

 when the evaporation commences, the water passes off 

 slowly into a series of rectangular basins, less deep, where it 

 continues to concentrate, after which it passes into a trench 

 which conducts it to the great wells, called the wells of 

 green water. Pumps then raise it into a second trench, 

 by which it is carried into another series of evaporating 

 basins, called interior heaters, from which it passes into the 

 reservoir, and from thence by a third trench into more 

 wells, called the salt wells. Here the sea water marks 

 22° to 24° of Beaume's areometer. The pumps then pass 

 it into a fourth trench, which carries it into new basins, 

 smaller than the preceding ones, called salt tables. In 

 these tables, where the liquid mass is not above five or six 

 centimetres of depth, the salt is deposited. When the 

 principal part of the water has left the product, the water 

 is carried off by the canal to the sea, and a fresh quantity 

 of condensed salt-water is brought into the salt-pans. 

 The water is renewed daily or every two days, and this 

 operation is carried on during all the fine weather, that is, 

 from April to September. When the bed of salt is of the 

 thickness of four or five centimetres, it is collected .or 

 shovelled up. For this purpose the masses of salt are left 



