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(ion would have exifted, had the beds of rock-falt in this 

 diftridl been formed by the evaporation of fea-water inun- 

 dating the land at certain intervals of time, as the above 

 theory fuppofes ? On the contrary, fays he, would it not 

 be natural to expeft trom rcafonings, a priori, that the fait, 

 thus depoiited from fea-water, would be difpofed in layers 

 perfectly regular, and differing from one another merely in 

 thicknefs, or a few other circuuiftances of inferior mo- 

 ment ? 



Another fatfl which, it is fuppofed, invalidates, in fome 

 meafure, the notion that the rock-falt has been depofited 

 from the waters of the fea, is the great difproportion of 

 quantity, fhewn by analyfis to exift, between the earthy 

 falts contained in the brine of this diftrift, and thofe held in 

 folution by fea-water ; the ratio here being as one to ten, 

 or the proportion which the earthy falts bear to the pure 

 muriate of foda in fea-water is ten times greater than that 

 which prevails in the Chefhire brine. The afcertaining of 

 this faft proves, it is fuppofed, that the rock-falt (from the 

 folution of which the brine is formed) is combined with a 

 much fmaller proportion of earthy falts than exifts in fea- 

 water ; a circumftance difficult to be accounted for, on the 

 luppofition that the beds of this fubftance were formed by 

 the evaporation of the fea-water, occupying the vallies and 

 lowed parts of the land. It mult be noticed, however, as 

 worthy of attention, that the earthy falts, intermixed with 

 the rock-falt in the above diftricl, are the fame which are 

 held in folution by fea-water, being principally muriated 

 magnefia and fulphate of lime. 



There is, however, a ftill flronger proof, it is fuppofed, 

 againfl the notion that the beds of rock-falt in this county 

 are depofitions from the fea-water, in the circumftance that 

 no marine exuvias have ever been difcovered in the ftrata. 

 This, it is imagined, would almolt indubitably have been 

 the cafe, had the land been covered with fea-water during a 

 period of fufficient length for the depofition of beds of fait 

 of fuch prodigious thicknefs ; and the fadt, that no fuch 

 exuviae do actually exift, is fuppofed in itfelf fufficient to 

 induce a fufpicion that the theory in queilion cannot be 

 well founded. Other objections too, it is obferved, offer 

 themfelves to its validity ; fuch as the enormous depth of 

 fea-water neceflary to the production of a body of rock-falt 

 forty yards in thicknefs ; the difficulty, if not impofhbility, 

 on fuch principles, of accounting for the formation of the 

 lingular infulated mountain of rock-falt at Cordova, in Spain ; 

 with others of a more trivial nature, which will readily prc- 

 fenl themfelves in this inquiry. 



It is, however, at the fame time candidly acknowledged, 

 that there are many facts and circumftanc.es of adtual ob- 

 fervation, that confer a ftrong degree of plaulibility on the 

 opinion, againfl which it has been contended. The cer- 

 tainty that the furface of the county was at fome former 

 period much lower than it is at prefent, and the diminution 

 of the thicknefs of the ftrata of rock-falt in proportion as 

 they recede from the fea, are cireumftances which un- 

 doubtedly range themfelves on this fide of the queftion : 

 and, upon the whole, it is thought, that it may be doubted 

 whether the theory, which regard:, the beds of rock-falt as 

 depolits from fea-water, docs not accord more exactly with 

 exifting appearances, than any other which has been ad- 

 duced on the matter. 



It is fuppofed that many things, which at firft feem ob- 

 jections, may be obviated by a reference to the principles of 

 the Huttonian theory of the earth, and the excellent illuf- 

 tratious of it by profcflor Playfair. However, in the pre- 

 fent ltate of our knowledge, any opinion formed on the 



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matter muft, it is imagined, from its very nature, be purely 

 theoretical. See RocK-Sa/t Pin. 



RoCK-Salt Pits, fuch pits, fhafts, mines, or openings, 

 as are dug or made in any other manner in the ground,' 

 for the purpofe of getting and raifing rock-falt from them. 

 Pits of this fort are met with in many parts of the county 

 of Cheftcr, which are wrought to very confiderable extents, 

 and are of great importance to the interefts of the diftrift 

 in many different ways, as well as to the nation in general, 

 as may be feen under the head RocK-Salf. 



According to the ftatement of Mr. Holland, in his 

 Agricultural Survey of the above county, the firft bed 

 and pit of falt-rock was found and wrought in Marburv, 

 at a fmall diftance from the town of Northwich, at the 

 depth of about thirty yards from the furface, in the year 

 167c, when fearching for coal. The bed was thirty yards 

 in thicknefs, and relied upon a ftratum or layer of hard 

 clay. In confequence of this difcovery, other fimilar at- 

 tempts were made; and on finking fhafts or pits any where 

 in the vicinity of it within the fpace of half a mile, it was 

 found to exiit at about the fame depth from the furface of 

 the earth, when, not prevented from being dug down to by 

 brine-fprings or thofe of common water. This continued the 

 only place in which it was found until the year 1779, when 

 this fort of rock was again met with in fearching for brine 

 in the neighbourhood of Lawton, at the depth of about 

 forty-two yards, hut only of the thicknefs of about four 

 feet ; there being beneath it a bed of indurated clay ten 

 yards in thicknefs which being penetrated through, a fecond 

 ftratum of rock-falt was difcovered twelve feet in thick- 

 nefs ; and on continuing the finking of the pit, another 

 layer of indurated clay, fifteen yards in thicknefs, was 

 pafL'd through ; below which appeared a third ftratum of 

 rock-falt, which was funk into not lefs than twenty-four 

 yards ; the loweft fourteen yards, being the pureft, or the 

 leaft mixed witli other fubftanccs, were the only parts that 

 were wrought. 



Until this period, in the neighbourhood of Northwich, 

 no attempts had, however, been made to fink pits in order 

 to find a lower ilratum of rock-falt ; as the one which had 

 been firft met with was fo thick, and furnifhed fuch an 

 abundant fupply for every demand, there could be no other 

 inducement to this than the expectation of meeting with a 

 ftratnm, at a greater depth, which might contain a lefs ad- 

 mixture of earthy matters. It would feem, too, that the 

 fear of meeting with fprings below, which might impede 

 the working out oi~ the materials from the pits, and even 

 render this wholly impra&ii ibl ted the ['roprictors 



of them from linking deeper. As, however, no inconveni- 

 ence or interruption of this nature had occurred, on fink- 

 ing through different alternate ftrata of rock-falt and 

 clay at Lawton ; and it had been found that there was 

 a lower ftratum of rock-falt there, which was more pure 

 than thofe nearer the furface, the owners of one of the 

 works or pits in this vicinity were induced, a little time 

 after the trials at Lawton, as in 17S1, to (ink deeper 

 than had yet been done, and to pals through the bed 

 or body of indurated clay lying underneath the rock-falt, 

 which had been fo long known and This 



indurated clayey material was : •:: . I I 1 !<" from ten 



to eleven yards in thicknefs; and immediately beneath it a 

 fecond ftratum of rock-falt w 1 ith, the. upper part 



of which diflered little in purity from that of the litirh'-r 

 ftratum or layer of rock ; but on penetrating into it to the 

 extent of horn twenty to twenty-five yards, it was there 

 found to be much more pure and free from earthy admix- 

 ture. 



