i88o.] 
Salt Industry of England. 
157 
expected to rise, the bottom pipe having holes in it to let 
out the brine when it is tapped. Being thus equipped, a 
set of boring rods is let down each pipe, and the remaining 
strata at the bottom of the cylinders are bored through into 
the brine. On being thus tapped, the brine rises up the 
bore hole, and, entering the pipe, passes through the holes 
near the bottom into the cylindered shaft, where it rises to 
its level. Provision is also sometimes made by having a 
plug, or a tap, at the bottom, below the holes in each pipe, 
so that if needed the entry of the brine into the shaft may 
be stopped, and the shaft emptied. In the brine shafts, 
where brine is pumped out of the old rock salt mines and is 
met with at a much higher pressure than in the rock-head 
brine shafts, the tapping has been attended with extra- 
ordinary difficulties. The brine in these old workings rises 
to as high a level as the brine that is found at the rock head, 
and as it has to be tapped through a pillar near the bottom 
of the old workings, the pressure is proportionately higher. 
It seems to have been long noticed that in Cheshire the 
Northwich brine contained a trace of iron, and that the 
earthy salts were the same which were held in solution by 
sea water, being principally chloride of magnesium and 
sulphate of lime ; the proportion of the earthy salts to pure 
chloride of sodium in sea water being greater than that 
which prevailed in the brine. Analyses made in 1808 of 
various brine springs showed that the percentage of chloride 
of sodium and of earthy salts in one pint of brine varied 
from 26*566 to 21*250 of the former, and from 2*500 to 0*625 
of the latter. 
The brine, on being pumped from the pits, is run into 
large cisterns, or into reservoirs, made sufficiently high for 
the brine to flow by gravitation through pipes as it is required 
in the evaporating pans. It is there evaporated upon one 
general principle. The heat for the evaporation is usually 
supplied from coal fires beneath, but sometimes the spare 
heat from a steam boiler is used after it has passed the 
boiler, or the discharged steam from an engine is sometimes 
utilised in the same way ; and, occasionally, there are pipes 
with steam in them amongst the brine in the pans. In this 
way, according to the different degrees of heat applied, the 
produdl is large or small grained salt. For what is called 
lumped, or fine grained salt, the brine in the pan is brought 
to a temperature of 226° Fahrenheit, which is the boiling 
point for brine. Crystals soon form on the surface, and 
after skimming about a little they subside to the bottom. 
Each crystal appears granular or a little flakey, and is in 
