17 
Brine is formed by fresli water reaching the surface of 
the salt either at the so-called outcrop or through fissures 
and faults in the marl. The marl itself, when unfissured or 
undisturbed, is perfectly impermeable. It is pretty certain 
that the water gains admission at a higher level than the 
rock salt, for the brine originally rose nearly to the surface 
of the ground in some districts, and in others rose many 
yards up the shaft when the “ flag” was pierced. Brine is 
only met with on the surface of the Top Bock salt, which salt 
averages about 25 yards in thickness in the neighbourhood of 
North wich. At Winsford the Top Bock salt lies more than 60 
yards from the surface, and is rather thicker than at North- 
wich, though the indurated clay separating the two beds of 
salt is about the same thickness. The bottom bed of rock 
salt is about 35 yards thick at North wich and rather more 
at Winsford. No water is ever found on this salt. The 
“ Bock Head,” as it is called, is perfectly dry. 
It is almost impossible to say what the area of these beds 
of rock salt is. Judging, however, by the subsidence of 
the land, and taking into consideration the furthest points 
at which salt has been proved by shafts, I have come to the 
conclusion that the Northwich beds occupy at least three 
square miles, and contain in the aggregate about 900,000,000 
tons — the upper bed 380,000,000, the lower 520,000,000. 
The Winsford district is more difficult to determine, but, 
being again guided by the distinct subsidences of the land, 
there cannot be less than six miles of salt beds containing 
at least 1,900,000,000 tons of salt. It is quite impossible to 
estimate the quantities of rock salt in the Nantwich, Middle- 
wich, and Lawton districts, as there are no mines; and only 
in Lawton has the salt rock been bored through. There 
are several other districts where salt must exist as is shown 
by the subsiding of the land. The figures given, which • 
are the merest approximations, show that practically the 
salt beds are inexhaustible. 
