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BALANCE.

of cobalt, which precipitates upon mixing the two solutions, is the preparation of cobaltmost suitable for painting upon porcelain, and for the manufacture of blue glass. SeeCobalt.

B.

BABLAH. The rind or shell which surrounds the fruit of the mimosa cineraria ; itcomes from the East Indies, as also from Senegal , under the name of Neb-neb. It con-tains gallic acid, tannin, a red coloring matter, and an azotized substance; but the pro-portion of tannin is smaller than in sumach, galls, and laioppern (gall-nuts of the commonoak) in reference to that of gallic acid, which is considerable in the bablah. It has beenused, in dyeing cotton, for producing various shades of drab; as a substitute for the moreexpensive astringent dye-stuffs.

BAGASSE . The sugar-cane, in its dry, crushed state, as delivered from the sugar-mill. It is much employed for fuel in the colonial sugar-houses.

BAKING. (Cuire, Fr. Backcn , Germ.) The exposure of any body to such a heatas will dry and consolidate its parts without wasting them. Thus, wood, pottery, andporcelain, are baked, as well as bread.

BALANCE. To conduct arts, manufactures, and mines, with judgment and success,recourse must be had, at almost every step, to a balance. Experience proves that allmaterial bodies, existing upon the surface of the earth, are constantly solicited by a forcewhich tends to bring them to its centre, and that they actually fall towards it when theyare free to move. This force is called gravity. Though the bodies be not free, the ef-fort of gravity is still sensible, and the resultant of all the actions which it exercises upontheir material points, constitutes what is popularly called their ucighl. These weightsare, therefore, forces which may be compared together, and by means of machines maybe made to correspond or be counterpoised.

To discover whether two weights be equal, we must oppose them to each other in amachine where they act in a similar manner, and then see if they maintain an equi-librium; for example, we fulfil this condition if we suspend them at the two extremitiesof a lever, supported at its centre, and whose arms are equal. Such is the general ideaof a balance. The beam of a good balance ought to be a bar of well-tempered steel, ofsuch form as to secure perfect inflexibility under any load which may be fitly appliedto its extremities. Its arms should be quite equal in weight and length upon each sideof its point of suspension ; and this point should be placed in a vertical line over thecentre of gravity ; and the less distant it is from it, the more delicate will be the balance.Were it placed exactly in that centre, the beam would not spontaneously recover thehorizontal position when it was once removed from it. To render its indications morereadily commensurable, a slender rod or needle is fixed to it, at right angles, in the linepassing through its centres ot gravity and suspension. The point, or rather edge ofsuspension, is made of perfectly hard steel, and turns upon a bed of the same. Forcommon uses the arms of a balance can be made sufficiently equal to give satisfactoryresults; but, for the more refined purposes of science, that equality should never bepresumed nor trusted to; and, fortunately, exact weighing is quite independent of thatequality. To weigh a body is to determine how many times the weight of that bodycontains another species of known weight, as of grains or pounds, for example. Inorder to find it out, let us place the substance, suppose a piece of gold, in the left handscale ol the balance; counterpoise it with sand or shot in the other, till the indexneedle be truly vertical, or stand in the middle of the scale, proving the beam to behorizontal. Now remove gently the piece of gold, and substitute in its place standardmultiple weights of any graduation, English or French , till the needle again resumes thevertical position, or till its oscillations upon either side of the zero point are equal.These weights will represent precisely the weight of the gold, since they are placed inthe same circumstances precisely with it, and make the same equilibrium with the weightlaid in the other scale.

This method of weighing is obviously independent of the unequal length ns well asthe unequal weight of the arms of the beam. For its perfection two requisites only areindispensable. The first is that the points of suspension should be rigorously the samein the two operations; for the power of a given weight to turn the beam being unequal,according as we place it at different distances from the centre of suspensior, did thatpoint vary in the two consecutive weighings, we would require to employ, in the second,a different weight from that of the piece of gold, in order to form an equilibilum withthe sand or shot originally put in the opposite scale; and as there is nothing to indicatesuch inequality in the states of the beam, great errors would result from it. The bestmode of securing against such inequality is to suspend the cords of the scales fromsharp edged rings, upon knife edges, at the ends of the beam, both made of steel so