Page:Theophrastus - History of Stones - Hill (1774).djvu/345

 to the Senes, that Copper was capable of giving the deepet and finet Blue imaginable) was made, was a volatile alkaline Spirit: And where Nature could find, in the Bowels of the Earth, any Thing analogous to a volatile urinous Alkali, produced by Chemitry, was a Quetion not eaily anwered. The particular Salt of the mineral Waters eems to approach, indeed, omething to a Mentruum of this Kind; and Dr. Hoffman has proved, that it is at leat much fitter to be claed with the Alkalies than with the Acids. But the Sytem of the Colours of the blue Gems being from Copper, mut tand upon a very precarious Bais, if there could be found no other Mentruum than one we are o very uncertain about, to trike their Colour from that Metal.

Copper, however, is, in Truth, perhaps the farthet of all the Metals from being ubject only to the Power of one appropriated Mentruum; and a Coure of Experiments on it, have now hewn me, that we need not have Recoure to o uncertain a mineral Subtance as this latent Alkali, for producing a Blue from it; but that Mentruums of another Kind, even Acids, and thoe the very Acids, whoe Principles are the commonet of all others in the Earth, can afford us the ame Colour; and are every where to be found in great Abundance. Gold is oluble only in Agua regia; for all the other Mentruums that are talked of for it, have a genuine Sea-alt for their Bais, and are therefore only o many Kinds