MANUFACTURE OF SALT IN CHESHIRE. 15 



lower than in 1865. It is evident that more brine is being 

 pumped out than fresh water getting in to make new brine 

 to replace it. Many shafts have been completely exhausted. 



Of late years a number of old worked-out mines in the 

 lower bed of rock salt have been used as reservoirs, into 

 which the brine from the rock-head runs night and day. 

 These enormous reservoirs are nearly always full ; in the 

 majority of cases the brine rises high up the shafts. The 

 mines in the bottom rock vary from 100 to 112 yards 

 from the surface, and the salt is worked out to a depth of 

 about 15 feet. Some of these reservoirs will hold more than 

 50,000,000 gallons of brine. Every day the trade consumes 

 more than 4,000,000 gallons in making white salt. This 

 enormous consumption has produced very startling results, 

 which I shall refer to later on. The brine is pumped up 

 by means of powerful steam-engines into reservoirs or tanks, 

 and from these it is distributed to the pans through pipes. 



The specific gravity of fully saturated brine is about 1*2 ; 

 and it contains 26 per cent, of salt. Roughly speaking, 

 the Cheshire brines consist of 1 part salt, 3 parts water. 

 The business of the salt-manufacturer is to drive away the 

 water and to retain the salt. This is done by heat ; and 

 the rationale of the process of making salt is extremely 

 simple. When brine is fully saturated there is a state of 

 equilibrium, as it were. If we reduce the quantity of water, 

 this balance is disturbed, and a portion of the salt crystal- 

 lizes out, until the brine is again at saturation-point. If 

 we continue driving off the water, the salt continues to 

 crystallize and deposit. This process might go on till all 

 the water was expelled and all the salt crystallized ; but 

 in the process of manufacture this never occurs, as the pan 

 is replenished with brine from time to time. 



During the manufacture of salt the laws regulating the 

 formation of salt crystals may be clearly seen. The kinds 



