Mr. H. Holland on the Cheshire Rock-salt District. 45 



salt manufacture will be sufficiently obvious from the statement, that 

 besides the salt made for home consumption, which annually amounts 

 to more than 16,000 tons, the average of the quantity sent to Liver- 

 pool for exportation has not been less than 140,000 tons. 



General situation, thickness , ^c. of the beds of rock-salt. 



Though springs impregnated with salt occur in several parts of 

 - the Cheshire plain, it may be remarked that the rock-salt itself has 

 only been worked into near the banks of the Weaver and its tribu- 

 tary streams. It was first discovered at Marbury near Northwich, 

 about one hundred and forty years ago, in searching for coal. 

 This bed of rock was the only one worked for more than a century, 

 when, in the same neighbourhood, a second and inferior stratum was 

 met with, separated by a bed of indurated clay from the one pre- 

 viously known. This lower stratum was ascertained to possess at a 

 certain depth a great degree of purity and freedom from earthy ad- 

 mixture ; on which account, and from the local advantages of North- 

 wich for exportation, the fossil salt is now worked only in the vici- 

 nity of this place. 



This local limitation of the mines precludes the possibility of 

 many comparative remarks which might be interesting to the geolo- 

 gist ; and in giving a particular description of the rock-salt formation, 

 I must confine myself in great measure to the facts which present 

 themselves in the neighbourhood of Northwlch, explaining first the 

 circumstances of general position, &c. and then entering into the 

 more minute particulars of the mines which have been sunk into 

 these important strata. 



The rock-salt of Northwlch occurs, as I have just mentioned, in 

 two great strata or beds, lying nearly horizontally, but on different 

 levels, and separated, the superincumbent from the subjacent stratum, 



