Analysis of British and Foreign Salt, * IOT 



former case, whether any chemical difference can be dis- 

 covered, that may explain the superiority of the one to the 

 other. ' 



The comparative fitness of these varieties of salt for the 

 curing of provisions, which has been a subject of much 

 controversy among the parties who are interested, can be 

 decided, it is obvious, in no other way, than by a careful 

 examination of the evidence on both sides. Where evi- 

 dence, however, is doubtful, and where there exists, as in 

 this case, much contrariety of testimony, it cannot be un- 

 fair to yield our belief to that which best accords with the 

 chemical and physical qualities of the substances in ques- 

 tion. Again, if salt of British production should be 

 proved to be really inferior in chemical purity to foreign 

 salt, it would be important to ascertain, as the basis of all 

 attempts towards its improvement, in what, precisely, this 

 inferiority consists. It seemed desirable, also, to examine 

 whether any di [Terences of chemical composition exist 

 among the several varieties of home-made salt, which can 

 explain their variable fitness for ceconomical purposes. 



Such were the considerations that induced me to under- 

 take an inquiry, which has occupied, for several months 

 past, a large share of my leisure and attention. I began 

 the investigation, wholly uninfluenced by any precon- 

 ceived opinions on the subject ; and I had no motive 

 \o see the facts in any other than their true light, since I 

 have no personal* interest, either directly or remotely, in 

 the decision of the question. 



The principal sources of the salt, which is manufactured 

 in this country, are rock salt, brine springs, and sea water. 

 The first material is confined entirely, and the second 

 chiefly, though not wholly, to a particular district of Che- 

 shire. Of the extent and boundaries of this district, the 

 process of manufacture, and other circumstances interest- 

 ing to the mineralogist as well as to the chemist, an ample 

 and excellent history has feeen given by Mr. Henry Hol- 

 land, in the agricultural report of the county of Chester*. 

 Prom hi:* account, I shall extract, in order to render some 

 parts of this memoir more intelligible, a very brief state- 

 ment of the characteristic differences of the several varieties 

 of salt, which are prepared in Northwich and its neigh- 

 bourhood. 



In making the stoved or lump salt, the brine is brought 

 to a boiling heat, which,, in brine fully saturated, is 226^ 



* Published in 1808. 



of 



