"The word nitre had been applied by the ancients to carbonate of soda, a production of Egypt, where it is still formed from sea-water by some unknown process of nature in the marshes near Alexandria. This is evident not merely from the account given of it by Dioscorides and Pliny; for the following passage from the Old Testament, shows that it had the same meaning among the Jews: "As he that taketh away a garment in cold weather, is as vinegar upon nitre: so is he that singeth songs to a heavy heart." Vinegar poured upon saltpetre produces no sensible effect whatever, but when poured upon carbonate of soda, it occasions an effervescence. When saltpetre came to be imported to Europe, it was natural to give it the same name as that applied to carbonate of soda, to which both in taste and appearance it bore some faint resemblance. Saltpetre possessing much more striking properties than carbonate of soda much more attention was drawn to it, and it gradually fixed upon itself the term nitre, at first applied to a different salt. When this change of nomenclature took place does not appear; but it was completed before the time of Roger Bacon, who always applies the term nitrum to our nitrate of potash and never to carbonate of soda."