On the Extraction of Salts from Sea-Water. 101 



The waters of the Mediterranean contain, according to the 

 analysis of Usiglio, about three per cent, of common salt, while 

 those of the Atlantic contain from 2.5 to 2.1 per cent. In 

 the waters of the Mediterranean there are besides, about 6.8 

 per cent, of sulphates and chlorids of calcium, magnesium and 

 potassium. The quantity of water which it is necessary to evapo- 

 rate in order to obtain a small amount of salt, thus appears to be 

 very great, but under favorable circumstances this is a small consi- 

 deration, as will appear from the following fact. The saline of 

 Berre is situated upon a small lake, communicating with the 

 ocean, but fed by streams of fresh water, so that while the waters 

 of the open sea have a density of 3°5, those of the lake have only 

 1°5, or scarcely half the strength of sea water. Nevertheless, the 

 advantages of the position offered by the shores of the lake for the es- 

 tablishment of a saline, are sufficient to compensate for the deficien- 

 cy of salt in the water, and to make of Berre one of the most flour- 

 ishing salines of the south of France. The evaporating surfaces here 

 cover 3,300,000 square metres, equal to 815 English acres; of this 

 area one-tenth is occupied with the salting tables, but with sea- 

 water, where less evaporation is required to bring the brine to the 

 crystallizing point, one sixth of the area would be thus occupied. 

 The amount of salt annually produced at the saline of Berre is 

 20,000,000 of kilogrammes. 



Owing to the dilution of the water of the lake of Berre, the 

 proportion of salt there manufactured is small when we consider 

 the area, and compare the produce with that of other salines 

 where pure sea-water is evaporated. According to Mr. Balard, 

 2,000,000 square metres may yield 20,000,000 kilogrammes annu- 

 ally ; and Mr. Payen states that the same amount of salt is 

 produced at Baynas from a superficies of 1,500,000 metre. As a 

 cubic metre of sea-water contains about 25 kilogrammes of salt, 

 the evaporation required to produce the above amount corresponds 

 to 800,000 cubic metres, equal in the second estimate given above, 

 to a layer of water 0.40 metre, or 15| English inches in thickness. 



The plan hitherto adopted in the salines of the European coastsi 

 nas been to commence the evaporation of the sea-water with the 

 spring time of each year ; in this way some three or four months 

 elapsed before a sufficiently large amount of strong brine was 

 accumulated to enable the manufacturer to commence the deposi- 

 tion of salt on the salting tables, and as this latter operation can 

 only be carried on in fine weather, the rainy season of autumn 



