Mr, A. B. Northcote on the Brine-springs of Cheshire. 461 
which served as reservoirs for the wich-houses*. From manual 
labour they passed to the employment of horses for this purpose ; 
water-power and windmills were subsequently used ; but all have 
been superseded of late years by the superior efficiency of the 
steam-engine. The methods of evaporation have also undergone 
vast extension and improvement. In early times this process was 
conducted in small leaden vessels, six of which they had in every 
house in Nantwich, and the salt was removed by women with little 
wooden rakes, placed in baskets, and drained+. These six leaden 
pans were afterwards exchanged for four iron ones, about 6 
inches in depth and of a surface of about a square yard, capable 
of holding the same contents as the original leaden vessels. The 
limited extent of the operations thus conducted diminishes our 
wonder at the great proportion of wich-houses existing at these 
places during the middle ages, and so far surpassing the number 
in operation at the present day. Even so recently as a century 
ago, the largest pans at Northwich were only 20 feet long by 9 
or 10 broad ; whilst those employed forty years since had a super- 
ficies of 600, 800 and 1000 feet, with a depth of from 16 to 18 
inches. The area of the pans has now, I suppose, almost reached 
its limit ; some which I saw at Mr. Blackwell’s works at Wheelock 
having a length of 70 feet and a width of 23 feet, making 
1610 feet of surface. The heat is generally applied directly by 
the flue of from one to three furnaces, placed at one extremity 
of the pan, but in the works of Messrs. Kay of Winsford, I 
found part of the evaporation conducted upon a different prin- 
ciple: a small iron pan, heated by a furnace in the ordinary way, 
is made to communicate by a narrow channel, with’a brick- or 
clay-lined basin ; this again is in connexion with others of the 
same description disposed around a centre, and lastly, one is 
arrived at immediately adjoining the first-mentioned iron pan ; 
the brine is here by a very simple kind of pump transferred to 
the heated iron vessel, by which means the level of the liquid in 
the brick basins is kept constantly below that in the original 
starting-place, and thus a continual circulation of the brine is 
maintained. 
In the preparation of salt from brine, various substances have 
been at different times added from the idea of improving the qua- 
lity of the product. Until recent times it was thought, that during 
the evaporation of an aqueous solution of chloride of sodium, hy- 
drochloric acid was expelled, and soda formed: this doubtless arose 
from the decomposition of the chloride of magnesium contained 
in the brine with which the experiments were made,—an evolu- 
tion of acid vapours having been probably observed during the 
* Tolland’s Agriculture of Cheshire, p. 48. 
t Ibid. p. 50, 
