The preparation of ox-gall to be used in marbling is simple. Take a quart of fresh bile (ox-gall or fish-gall), place in a bottle which contains when filled from 1-1/2 to 2 quarts, add 1/2 pint of absolute alcohol, shake well and leave stand for from 14 days to 3 weeks. Within this time all particles of gum and all fatty substances which are present in some galls in comparatively large quantities, will fall to the bottom and the gall will be thin-fluid, pure and diaphanous, brownish, yellow or greenish according to the nourishment of the animal from which it was taken. Cow-gall contains more gum and fatty substances, than ox-gall; fish-gall, on the other hand, is thinner than ox-gall and would be the most useful of them all, if it could be obtained in sufficient quantities. If the gall is thin and pure it is filtered through paper which is easily and quickly done as it runs like water. If by filtering the dregs of the gall the filter should become clogged, a new one must be used. The addition of alcohol causes the precipitation of glutinous and fatty substances and preserves the gall from decomposition. If prepared in such a way it can be preserved for years without spoiling. All colors which we intend to use for marbling must be bound to bodies absolutely insoluble in water; it is therefore a mistake to say, that the colors dissolve in water. You may grind the color on a marble slab or in a machine as long as you please, but you will only obtain a great degree of fineness of the bodies but never a dissolution of the same. Each body possesses its limit of divisibility; in amorphous bodies the high divisibility is but natural, but in crystalline bodies this division must be produced by grinding or washing. The gall does not combine with these bodies, nor does it penetrate them, but only clings to them loosely. It can be readily removed in case the colors should be rendered useless by the addition of too much gall. The color is allowed to precipitate in the bottle and the water standing above is poured off, fresh water is added and this manipulation is repeated several times. The gall which surrounds every particle of color forms, as it were, the support of it and adapts it to float upon the size. Bodiless colors, which give a complete solution with water will run into each other on being thrown on the size and will flow from the paper when it is lifted off. The insolubility of the color bodies therefore prevents them from running although they are disarranged on the size in drawing and although one color may be compressed or expanded by a second, yet they all remain separate without mixing, except, perhaps, that the shade of the first color becomes more intense, because its color particles are pushed together by the more violent expansion of the second color.