C 337 J

ions, to whom the comparisons were referred, differed mtheir judgements of them, and could not fix on any parti*cular coals as being more bluish, more truly black, ormore beautiful than the rest.

Instead of the small branches, I tried next pieces of dif-ferent woods, taken from the trunks of the trees. Herealso the several coals appeared alike among themselves,and scarcely differed in point of colour from those of thetwigs j but they seemed in general somewhat harder, anddid not mark quite so freely on paper when used a?crayons. Suspecting from hence that the hardness- of thecoal might be proportional to that of the subject it wasprepared from, I made some further trials, which seemedto confirm this notion. The coals of the hard woods,box and guaiacum, were very sensibly harder than thoseof the soft ones : the shells and stones of fruits yielded'■coals still harder, which would scarcely make any markon paper at all; while the coals of the kernels of fruitswere quite soft and mellow.

It may be judged from these experiments, that thepreference of one kind of wood to another for makingcharcoal crayons, does not depend so much upon any dif-ference of colour in the coals, as on their softness; in whichquality perhaps none of our common woods is equal to thewillow. Dr. Grew observes, in his anatomy of plants, thatin this wood the softness is equal or alike in all parts-whence the coal, when used as a crayon in painting, notonly makes the stroke light, but every where certain,without disturbing the even motion of the hand. Dealor fir is likewise a very soft wood, but of unequal soft-ness, so that when cut across, it tears, and will neverpolish or work smooth, whereas the willow works well'inall directions,

Horns,