40 Natural Hiftcry cf Salt. [Book VI. 



confifts of mere' water, the fluid which remains, is 

 consequently more concentrated. The operation is 

 then completed by means of artificial heat. 



Pure 



* Dr. Leigh, who firft {hewed the manner of refining rock fait, 

 informs us, that fome of the ftrongeft fprings at Northvvich, gave 

 feve-n or eight ounces of fait from a quart of brine ; but a quart of 

 brine weighs confiderably more thajs 32 ounces, the weight of a 

 quart of water : fo that the Northwich fprings, from this account, 

 do not yield a quarter of their weight. At Middlewich there is 

 faid to be one fait fpring, which is flronger than the reft, this fpring 

 yields a full fourth part of fait (K), and hence it is, probably, fully 

 faturated. We have an account in Kircher's works, of fome famous 

 brine fprings in Burgundy, from which we learn, that one hundred 

 pounds weight of the ftrongeft brine, gave twenty-five pounds, or 

 juft one fourth of its weight of white falt(7). 



1 There are a great many brine fprings in Chefhire, Worcefter- 

 fhire, StafFordfhire, Hampfhire, \and in other parts of Great Bri- 

 tain, fome of which are fufficiently rich in fait to be wrought with 

 profit, others not. From what has been before advanced, the 

 reader will readily comprehend that fixteen tons of the ftrongeft 

 brine confift of twelve tons of water, and of four tons of fait; and 

 that, in order to obtaifc thtfe four tons of fait, the twelve tons of 

 water rouft be, by fome means or oiher, evaporated, foas to leave 

 the fait in a concrete form. Suppofe there mould be a brine, 

 which in fixteen tons fhould contain fifteen tons of water, and only 

 er.e ton of fait; yet it may chance, that fuch a weak brine may be 

 wrought with more profit than the ftrongeft; for the profit arifing 

 from the boiling of brine into fait, depends as much upon the 

 price of the fuel ufed in boiling it, as ppon the quantity of fait 

 which it yields. Thus the fea-water, which furrounds the coafts 

 of Great Britain, is faid to hold feldom more than one thirtieth, or 

 lefs than one fiftieth part of common fait; but fuel is fo cheap at 

 Newcaftle, that they can evaporate thirty or forty tons of water, 



in 



jnto a little miftake, by confounding a pound of water with a 

 pound of brine; for if a pound or 16 ounces of water will only 

 diflblye 6 ounces of fait, a pound of the brine, thus formed, \vi$ 

 cnly hold 4> T ounces of fait. 



(/) Philbf. Tranf. N 53. 



(/) Kerch, Mun. Sub. Toto. JL Cap. XL 



