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deepest and darkest in its kind; and that, instead of takingone pigment for each colour, it is better to take as manyas can be got; for the greater contrast there is of hetero-geneous and discordant drugs, the more true and beautiful,he fays, will the black be, and the more capable of unitingwith all other colours, without suppressing them, and evenwithout making them tawney.

The trials I have made of mixing different blue, red,and yellow powders, have not succeeded so far as to afforda perfect black; but I have often obtained from themvery dark colours, such as may be called brown-blacksand grey-blacks, such as we commonly fee in the darkparts of paintings, and such as the charcoal and foot blacksappear when diluted a little. The ingredients being eachof a dark deep colour is a very necessary condition j forbright blues, bright reds, and bright yellows, mixed insuch proportions that neither colour prevailed, producedonly a grey. In effect, all compositions of this kind, phy-sically considered, can be no other than greys, or of some ofthe intermediate teints between whiteness and blackness ;and these greys will be so much the lighter or darker, asthe component colours of themselves are bright or dark.Some further experiments of producing a black by com-position, for the purposes of dying and staining, will bementioned in the sequel of this essay.

SECT. V.

Black paints , varnisnes , &c.

I. Black paint 'with oil.

B LACK oil paint is prepared, by grinding, with aproper quantity of oil, the charcoal or foot blacks,or the natural black earths, or pitcoal, till they are unitedinto a smooth, uniform, thick compound, which is occa-sionally