748 



SALT 



In those countries, as Portugal and the coasts of the Mediterranean, where sea-water 

 is used as the source of salt, a peculiar method of natural evaporation is resorted to, 

 in what are called ' Salt Gardens.' Large shallow basins, the bottom of which is 

 very smooth, and is formed of clay, are excavated along the sea-shore ; they consist 

 of: 



1st. A large reservoir, of from 2 to 6 feet in depth, communicating with the sea 

 by means of a channel provided with a sluice. Advantage is taken of the. high 

 tide to fill this basin ; and the water is allowed to remain here for some time to deposit 

 any suspended impurities ; it is then drawn off into the brine-pits. 



2ndly. The brine-pits are divided into a large number of compartments by means 

 of little banks ; these all have a communication with each other, but so arranged that 

 the water has a long circuit to make in its passage from one set to another ; it fre- 

 quently flows 400 or 500 yards before it reaches the extremity of this sort of labyrinth. 

 The various divisions are distinguished by a number of technical names. They should 

 be exposed to the north, north-east, or north-west winds. 



In the month of March the water of the sea is let into these reservoirs, where a 

 vast surface is exposed to evaporation from the first or clearing-working ; the others 

 are refilled as their contents decrease. The salt is considered to be on the point of 

 crystallising when the water begins to grow red ; soon after this, a pellicle forms on 

 the surface, which breaks and falls to the bottom. Sometimes the salt is allowed to 

 subside in the first compartment ; but generally, the strong brine is made to pass on 

 to the others, where a larger surface is exposed to the air ; in either case, the salt as 

 it forms is raked out, and left upon the borders to drain and dry. To get rid of the 

 chloride of magnesium, which is one of the principal impurities of this kind of salt, it 

 is frequently heaped lip under sheds, where it is just protected from the rain, and the 

 chloride of magnesium being a very deliquescent salt, attracts moisture from the air 

 and drains away. The salt thus obtained partakes of the colour of the bottom on 

 which it is formed, and is hence white, red, or grey. 



The following table shows the composition of several varieties of culinary salt : 



Analyses of several varieties of Culinary Salt. 



The specific gravity of a saturated solution of large-grained cubical salt, is 1-1962 

 at 60 Fahr. 100 parts of this brine contain 25'5 of salt (100 water + 34'2 salt). 



In Great Britain the rock-salt mines and principal brine-springs are in Cheshire ; 

 and the chief part of the Cheshire salt, both rock-salt and manufactured, is sent by 

 the river Weaver to Liverpool, a very small proportion of it being conveyed elsewhere, 

 by canal or land carriage. 



There are brine-springs in Staffordshire, from which Hull is furnished with white 

 salt, and the Worcestershire salt chiefly supplies the London market. 



Within the last few years, while boring for coal in the Cleveland district near 

 Middlesbro, Messrs. Bolchow and Vaughan discovered a considerable deposit of salt. 

 .Shafts are being sunk, not only at these works, but at the Clarence Works, belonging 

 to Messrs. Bell Brothers. In a short time wo may expect to find all the soda-works 

 npon the Tyne suppliedwith salt from those deposits in the North Biding of Yorkshire. 



According to M. Clement Desormcs, engineer and chief actionnaire of the great 

 salt-works of Dieuze, in France, the internal consumption of that kingdom is rather 

 more than 200,000 tons per annum, being at the rate of 6 kilogrammes for each 

 individual of a population estimated at 32,000,000. 



