phlogisticated muriatic acid, by aqua regia, and nitrous acid; but the other acids, being deficient in power to carry off the necessary quantity of phlogiston, do not take it up, unless it has been precipitated from some one or other of

these three.

But there is a substance, which, from its very deleterious qualities, it is highly necessary you should be made acquainted with; I mean litharge, that metallic substance formed out of the spume, foam, or froth of lead. It is found in furnaces where silver is refined, and hence, its name Aagyugos, that is, 2005 a stone, and agyugos silλιθαργυρος, λιθος ver. The litharge sold in the shops, is produced from copper works. Litharge is properly, lead vitrified, either alone, or with a mixture of copper. But lead is dangerous in a variety of instances, especially if employed in domestic vessels and utensils. Fountains and basons of it, in which water is kept, are often so noxious, as materially to hurt that element. The vapour and the powder of it are pernicious. But the saccharum saturni, sugar of lead, or ceruse, as it is commonly called, is of all, perhaps, the most pernicious. It is this property, unfortunately, which lead has of acquiring a sweet taste by a solution in acid, that has rendered it so serviceable to those venders of

VOL. I.

wine,

4

wine, who respecting their own profit more than the lives of their fellow creatures, have not scrupled to attempt to recover wines which have turned sour, by putting into them large quantities of ceruse, or litharge, a palpable poison. This offence is in Germany punishable with death. It is on account of the poisonous quality of litharge, that the use of white paint on the skin is found so destructive to the constitution.

As I have above said, however, of all metallic substances, iron is the most common. It is to be met with in the three kingdoms of nature. It is not only one of the principles which gives colour to plants, as well as to animals, but, when dissolved by the phosphoric acid, it always assumes a brilliant red colout itself. The ruby, the blood, and even wine, are each severally coloured by the combination of iron with the phosphoric acid. By variety in its combination, it always affords variety in tints. It was long a received opinion, also, as I have above remarked, that metals were not inhabitants of the primordial mountains. But, besides the familiar instance of Scotland,-at Scharfenberg, in Saxony, veins of silver are found in granite. Among the Pyrenees, the richest veins of

+

*Bishop Watson. + Sage. Charpentier.

lead

lead are found in the same rock. *

Nature,

therefore, is not so limited as has been supposed, in those mineral gifts which give to agriculture and arts their best instruments; to manufactures their best materials; and to commerce and society, the medium by which they are supported, and the chain by which they are linked.

And now I think we have looked at metallic substances in their most striking features. During our inquiries into the nature and properties of the permanently elastic fluids, we adverted to the lime, or the residuum of metals, acquiring a considerable degree of weight. We then saw, that it was heavier than the metal itself, previous to calcination. Astonishing

assuredly it is, that a body shall augment in weight, by losing one of its constituent parts. But the fact seems to be as M. Macquer argues, that metals cannot lose their phlogiston and calcine, but in proportion as the pure air of the atmosphere is precipitated and united to their substances; and that they are not reduced until the phlogiston, aided by heat, disengages the pure air. Chymists have looked upon rust as the lime of metals.

VOL. I.

Hh

The

* Dietrick.

The wild idea of making the most perfect of all these metals, gold, existed among the Egyptians and the Greeks, and was found among the Arabs, when the English, French, Germans, and Italians, went to the Holy Land, during the Crusades. From the 11th to the 16th centuries, it was carried to the most extravagant excess will you believe it, that within these six centuries, more than six thousand volumes have been published on the Elements and Practice of Chymistry; or the greatest part of them, more properly speaking, on the best means of artificially making gold? The contrariety of ideas on the subject of mineralogy, even from the year 1730, hath been astonishing. You cannot but have heard of Bromel, Linnæus, Cramer, Wallerius, Cronstedt, Woltersdorff, Gellert, Cartheuser, Justi, Lehman, Vogel, Stahl, Bergman, Scheele, Baumer, Valmont de Bomare, Buffon, Bucquet, D'Aubenton, Hill, Sage, De Saussure, Kirwan, Romè de l'Isle, Monnet, and multitudes of others.

At the same time you are not to forget, that gold was formerly used very plentifully in medicine. This remedy was particularly much in fashion in the 15th century.. The goodness

has

has at all times b een proportioned, you know, to the dearness of the drug. Bernard de Palissy exclaimed strongly against the Apothecaries of his time, who demanded ducat gold from the sick to put into their medicines, under the pretence, that the purer the gold, the more speedy would be the restoration of the health of the patient. Alchymy was therefore defined, ars sine arte, cujus principium est mentiri, medium laborare, tertium mendicare. But there was a class of Alchymists, whose genius, probity, and conduct, we have reason to venerate. They enriched chymistry with the best products we are acquainted with. Nor are we to treat disrespectfully, the study of that mineral kingdom whence the wants and conveniences of man are so amply supplied. And now I will relieve you from the subject, with just remarking, that gold is chiefly found in larger and smaller grains, blended with the composition of the rock; and this is the reason why so much gold dust, and grains, are found in the beds of rivers: and that lead, copper, and other ores, are found generally in the composi tion or fissures of the solid body of the rock. Allow me also just to mention to you, two or three metallic phænomena. For instance, a plate of copper, immersed in a solution of silver diluted in water, precipitates the metal. The Hh2 silver