and remain very obscure at last. We find certain effects produced and reason upon them, but so small are the parts operated upon, minute the agents, and equivocal the connexion, that we can do little more than theorize upon the subject; but perhaps I may slightly instance the difference existing in the fibre of flax and silk. The parts which compose the filaments of the former are generally considered as being flat and flaky, whereas those of the latter are tubular and round: this conformation renders silk so soft to the touch, and refracting more perfectly the rays of light, occasions much of its lustre, and the brilliancy of its hues. Perhaps we have no art or trade less confined within the trammels of formulæ than that of the dyer; every professor appearing to have his own methods of acquiring particular tints and shades, guided often in his proportions by that mutable sense, the taste, and regulating the temperature of his compositions, not by the thermometer, but by the feeling of the hand;—and so capricious are these tests, so different the sensations of the operator, or the variable influences of solar light, that success on one day does not insure a similar result on another. Color is probably only reflected light; but by what means the absorption of oxygen increases the lustre is not quite obvious—yet the power of the sun’s rays, in augmenting the intensity of the hues of many things, is well known: there is an admirable green color for foliage, to be obtained by the union of the light Prussian blue with the dark gamboge; but I could never acquire this clear and lustrous, without compounding it in the light of the sun. As the young artist will find this a most useful pigment, I may in addition say, that a small bit of the light Prussian, with three or four times the quantity of gamboge, must be laid upon the pallet, or in the saucer, and with a drop or two of water, only enough to make it work easily, be most thoroughly united and incorporated by the finger, with the sun shining upon the mixture, adding more gamboge repeatedly during the operation, until the blue is subdued and a clear green produced; but if a tedious operation, yet perseverance will ultimately produce a very brilliant permanent green.