12 MR. THOMAS WARD ON THE 



met with either above or below the main beds, we may say 

 there are two thick beds of rock salt, known locally as top- 

 rock salt and bottom-rock salt. These two beds are 

 separated by a layer of marl much indurated and contain- 

 ing veins of salt running nearly vertically, as if occupying 

 rifts, or cracks, or crevices in the hardened marl. This 

 layer is about 30 feet thick. The first bed of rock salt, or 

 the "top rock/' is at Northwich from 40 to 80 yards 

 from the surface, varying with the different surface-levels 

 and dipping from N.E. to S.W. The surface of this 

 salt bed is very irregular, being waterworn and channelled 

 as if by miniature streams. In most cases, immediately 

 before reaching the salt a much indurated marl is found, 

 locally termed " flag." On piercing this flag brine was 

 met with in the first instance, and continues so to be to 

 the present day *. 



Brine is formed by fresh 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-rock 

 salt, which salt averages about 25 yards in thickness in 

 the neighbourhood of Northwich. At Winsford the top- 

 rock salt lies more than 60 yards from the surface, and 

 is rather thicker than at Northwich, though the indu- 

 rated clay separating the two beds of salt is of about the 

 same thickness. The bottom bed of rock salt is about 

 35 yards thick at Northwich, and rather more at Winsford. 



* At Nantwich this " flag " has been met with in a boring for brine now 

 being carried on. 



