is not purely the genuine Effect of the Menſtruums, but a Change wrought in the Solutions made by them, by Particles of adventitious Salts floating in the Air; and mixing with a ſmall Quantity of them. Theſe Changes of Colour in the Solutions of Copper from an Admixture of Salts of a different Kind, tho' but in ſmall Quantities, we ſhall ſee hereafter in this Letter are very natural and eaſily producible Effects; and we need not wonder at a ſmall Quantity of an Ærugo of this Kind floating on the Surface of the Menſtruum, or affixed to a Plate of Copper, wetted with it, and expoſed to the Air, tho' the true Solution of Copper in the Menſtruum is blue; when we confider, that a Solution of the blue Vitriol in a Water impregnated with Sal Armoniac is green, notwithſtanding that a ſimple Solution of Copper in that Salt is blue; (ſfuch is the endleſs Variety reſulting from Mixtures of Salts as Menſtruums) and that the natural Ærugo produced on Copper by the Salts floating in the Air, is green.
It is not to be wondered at, that the Solutions of Copper in the fixed Alkalies produced from different vegetable Subſtances, are no way different from one another, ſince theſe Bodies act in theſe Solutions, not as the peculiar Salts of this or that Plant, but as a Body made, not by any Operation of Nature, but by the Effect of Fire; which has ſtrongly united the eſſential Salt, the Earth, and ſome ſmall Portion of the Oil of the Vegetable they have
been
