33 Mode of obtaining Salt [Book VI. 



employed to feparate the fait from fea-water. The 

 water is expofcd in trenches on the fea-fhore, where ic 



forms 



feventy thoufand pounds a year, or a tenth part of the whole 

 duty (6). 



1 The Northvvich rock fait is never ufed at our tables in its crude 

 flate ; and its application to the pickling or curing of fleih or fiih, 

 or preferving any pFOvifions, without its being previoufly refined 

 into white fait, that is, without its being diifolved in water, and 

 boiled down into what is called white fait, is prohibited under a 

 a penalty of 40 s. for every pound of rock fait fo applied. The 

 pure transparent TO a fie s, however, of rock fait, might, probably, 

 be ufed by us with our food, without any fort of danger or incon- 

 venience ; at lead, we know that rock fait is fo ufed, without be- 

 ing refined, both in Poland and in Spain. In the laft of thefe 

 countries, at Cordova in the province of Catalonia, there is a folid 

 mountain of rock fait, between four and five hundred feet in 

 height, and a league in circuit; its depth below the furface of the 

 earth is not known (c). This prodigious mountain of fait, which 

 has no mixture of other matter with ic, is efteemed fo fingular an 

 appearance, that it is thought to militate very much againfl the 

 opinion of thofe, who would derive the origin of all the beds of 

 rock fait, which are found under the furface of the earth, from 

 the evaporation of fait water, left in fubterraneous caverns, 

 either at the deluge, or upon iome more local commotions of the 

 globe. 



The quantity of rock fait which may be diffolved in a definite 

 quantity ,^fuppofe a pint or 16 avoirdupoife ounces of water, is 

 differently eilimated by different authors. Boerhaave is of opinion 

 that 16 ounces of water will not diffoive quite 5 ounces of rock 

 'falt(d'); Spielmann thinks that they will diflbive 6-y ounces (c) ; 



Newmann 



() Since I received this information, an additional duty of 

 lod. a bufhel has been laid, in 1780, on fait. The whole duty 

 now amounts to 4 s. zd. a bufljel, the btifliel weighing 56 llx. The 

 makers of fait can afford, in moft places, to fell their fait, exclufive 

 of duty, from 8</. to \&d. a bufhel. 



(r) Hill. Nat. de P Efpag. p. 406. See an account of fimilar 

 mountains of rock fait, in Shaw's Travels, p. 229, and in Pliny's 

 fJift. Nat. 1. xxxi. c. 7. 



(ct) Chem. vol. 1. p. 476. 



(t) Inft. Chem. p. 48. 



