E 338 3

Horns, and the bones both of fishes and of land ani-mals, gave coals rather glossier and deeper coloured thanthe vegetable coals, and which in general were very hard,so as difficultly or not at all to stain paper. It seemedhere, as in vegetables, that the hardness of the coal de-pends on that of the subject matter5 for silk, woollen*leather, blood, and the fleshy parts of animals, yieldedsoft coals. Some of these coals differed from others verysensibly in degree of colour : that of ivory is superior tothe rest, and is indisputably the finest of all the charcoalblacks. Indeed we have no black pigments equal inbeauty to ivory black, genuinely prepared, but some careis requisite in the choice of it, what is generally fold underthis name being no other than the coal of common bones.

On comparing the vegetable and. animal coals together,.in their lighter shades, on paper, the bluish cast, observedin all those, of the vegetable kingdom, was much less con-spicuous in those of the animal, many of which seemed toincline rather to brown than to blue. In the colour-ssiops a preparation is fold under the name of blue-black,which in this respect differs from the animal and agreeswith the vegetable coals, seeming to have no greater adegree of blueness than the coals of the. woods andtwigs above-mentioned, and even than common charcoal.,That this preparation is no other than. a vegetable coal,appeared from the following experiment, haid on-a redhot iron, it burnt , and glowed like powdered charcoal,and turned into white assies * which assies, thrown intooil of vitriol diluted with water, very readily diffolvedinto a bitterish liquor, the characteristic by which the ve-getable earth is distinguished. From what particularvegetable-matter,, this blue-black is prepared, experimentscannot discover; but those already mentioned seem suffi-cient-to shew, that it may be obtained from many, and

that,