152
duce, generally, is said to partake of the properties of thatbefore described, and also of that which is obtained, by theprocess of chymical art, from organized animal and vege-table substances. As the putrefaction of organized animals,under certain circumstances, is discovered to yield largeportions of nitrous acid, and as that acid, generally, readilycombines with calcareous earth, wherever it finds it, thiscombination being decomposed with fixed vegetable alkali,when the nitre produced from this process is called commonsaltpetre. Sometimes, also, it is discovered that nitrousacid is mixed with some one of the three calx before speci-fied, from which is procured a saltpetre known as cubicalsaltpetre.
These mineral calx, united with nitrous acid, are foundin several places in Europe, the East Indies, and America .
There is also a species of saltpetre brought to Europe from Egypt , as an article of commerce, which is said to beproduced in part by certain earths found in India, Africa ,and particularly Egypt , like that which covers the old rub-bish hills in the road between New and Old Cairo, and like-wise in numerous parts of Spain .
It has been conceived by authors, presumed to have beenwell informed themselves on this subject , 1 that this earthysaltpetre produced from extreme heat of solar efflorescence,was the only subject known as nitrum by the ancients.Which opinion appears probable, if the ancient nitre beconsidered to be what we at present call soda, as there isalso adequate room to suppose it partook of, at least, a verymaterial feature of this substance; because the sal nitrumof the ancients is found to have been used to cleanse inwashing generally; we have seen in a passage before citedon Feasts, that it was customary to wash with nitre aftersupper. Soap was not then discovered; this substance isstill used by our laundresses for the same purpose. Itsalkaline or dissolvent qualities, proclaiming its utility forthese purposes.
Originally, there is the largest extent for presumptiveproof, the ancients were content with only one or two re-sembling properties in substances, to give them one general
thousands poods from Astracan. Not far from the river Ueit, in Siberia , there islikewise a lake, where, in the summer, a third part of saltpetre is mixed with thecommon salt produced round its shores. In that place, wood being scarce, it willnot answer the cost to separate the saltpetre from the salt, which must be done byboiling. There is also much sulphur found in common rocks of talc, in the king-d6na of Casan , as fine and clear as amber. Strahfenberg's Hist.-Geog. Description ofNorth and-Nortk-East of Europe and Asia ,
* Particularly Professor Beckmann, vol. iv. p. 532.