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under the gold, and used also for the colouring os depressedparts where gold leaf cannot be conveniently applied. Thesubstance chiefly employed for this purpose is yellow ochre;the colour of which may be improved, or brought nearerto the gold teint, by a small addition of vermilion or otherred powders.

Of the mineral called auripigmentum or orpiment, somesorts are of a beautiful glittering gold colour. This mine-ral consists of arsenic and sulphur, and on being groundwith oil for painting, yields an offensive smell, as sulphuralways does when united with oils : this is the principal in-convenience it is accompanied with, and renders its use lessfrequent than it would otherwise be. Though it is offen-sive from the sulphur, the suspicion of its being poisonousin virtue of the arsenic appears to be without foundation,for the fetid vapour proceeds wholly from the sulphur, andeven arsenic in substance, if we may judge from trials madeon brutes, has its poisonous quality sheathed or destroyedby the combination of sulphur with it.

A beautiful gold coloured preparation, called aurum mo-Jhicum or musivwn, is obtained from tin. Some sine tin ismelted in an iron ladle; and half its quantity of pure quick-silver, previously heated in another ladle till it begins tosinoke, is poured into the melted metal, and the mixturestirred with an iron rod : when cold, the matter is foundfriable, and being reduced into sine powder, it is well mixedwith half or a third its weight of sal ammoniac and thesame^quantity of flowers of sulphur. With regard to theproportion of these ingredients, practical writers differ nota little, and indeed they admit of great latitude, for I havesucceeded equally with very different proportions : verylittle of any of them is retained by the tin in the subse-quent part of the operation. The powder is put into amatras, or round glass with a short neck, whch is placed in

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