9 * 
of British and Foreign Salt. 
The principal sources of the salt, which is manufactured in 
this country, are rock salt, brine springs, and sea water. The 
first material is confined entirely, and the second chiefly, 
though not wholly, to a particular district of Cheshire. Of 
the extent and boundaries of this district, the process of ma- 
nufacture, and other circumstances interesting to the minera- 
logist as well as to the chemist, an ample and excellent 
history has been given by Mr. Henry Holland, in the 
Agricultural Report of the county of Chester.* From his 
account, I shall extract, in order to render some parts of this 
memoir more intelligible, a very brief statement of the cha- 
racteristic differences of the several varieties of salt, which are 
prepared in Northwich, and its neighbourhood. 
In making the stoved or lump salt, the brine is brought to a 
boiling heat, which, in brine fully saturated, is 226° of Fah- 
renheit. This temperature is continued during the whole 
process ; and as the evaporation proceeds, small flakey crys- 
tals continue to form themselves, and to fall to the bottom of 
the boiler. At the end of from eight to twelve hours, the 
greatest part of the water of solution is found to be evaporated ; 
so much only being left, as barely to cover the salt and the 
bottom of the pan. The salt is then removed into conical 
wicker baskets, termed barrows ; and, after being well drained, 
is dried in stoves, where it sustains a loss of about one seventh 
of its weight. 
On the first application of heat to the brine, a quantity of 
carbonate of lime, and sometimes a little oxide of iron, both of 
which had been held in solution by an excess of carbonic acid, 
are separated ; and are either removed by skimming, or are 
* Published in 1808. 
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