620 PHILOSOPHICAL TRANSACTIONS. [aNNO 1748. 



it in such abundance, that there are few countries which do not afford vast 

 quantities of rock or fossil salt. Mines of it have been long discovered and 

 wrought in England, Spain, Italy, Germany, Hungary, Poland, and other 

 countries in Europe. The sea also affords such vast plenty of it, that all man- 

 kind might thence be supplied with quantities sufficient for their occasions. 

 There are also innumerable springs, ponds, lakes, and rivers impregnated with 

 common salt, from which the inhabitants of many countries are plentifully sup- 

 plied with it. 



In some countries, which are remote from the sea, and have little commerce, 

 and which are not blessed with mines of salt, or salt waters, the necessities of 

 the inhabitants have forced them to invent a method of extracting their common 

 salt from the ashes of vegetables. 



In short, this salt is dispersed all over nature; it is treasured up in the bowels 

 of the earth; it impregnates the ocean; it descends in rains; it fertilizes the 

 soil; it arises in vegetables; and from them is conveyed ir)to animals; so that it 

 may well be esteemed the universal condiment of nature. 



Naturalists, observing the great variety of forms under which this salt appears, 

 have thought fit to rank the several kinds of it under certain general classes, 

 distinguishing it most usually into rock or fossil salt, sea-salt, and brine or foun- 

 tain salt ; to which may be added others of those muriatic salts, which are found 

 in vegetable or animal substances. These several kinds of common salt often 

 differ from each other in their outward form and appearance, or in such acci- 

 dental properties as they derive from the heterogeneous substances with which 

 they are mixed; but, when perfectly pure, they have all the same qualities; so 

 that chemists, by the exactest inquiries, have not been able to discover any essen- 

 tial difference between them. It may for the present purpose be proper to dis- 

 tinguish common salt into the 3 following kinds, viz. into rock or native salt, 

 bay-salt, and white salt. 



By rock salt,* or native salt, is understood all salt dug out of the earth, 

 which has not undergone any artificial preparation. Under the title of bay-salt, 

 may be ranked all kinds of common salt extracted from the water, in which it is 

 dissolved, by means of the sun's heat, and the operation of the air ; whether the 

 water, from which it is extracted, be sea-water, or natural brine drawn from wells 

 and springs, or salt water stagnating in ponds and lakes. Under the title of 

 white salt, or boiled salt, may be included all kinds of common salt extracted by 

 coction from the water in which it was dissolved; whether this water be sea- 



• By rock salt, or sal rupiura, the ancient chemists mean salt adherina; to the rocks above the high 

 water mark, being there lodged by the spray of the sea, evaporated by the heat of the sun ; which 

 is the purest salt of all for chemical uses, and is to be had off the rocks of Sicily, and several islands 

 in the West Indies. C. Mortimer. — Orig. 



