Color

used in the drawings of fortification. It is nece ary to use colors in the drawings of plans and profiles of a fortification, in order to distinguish every particular part, and separate, as it were, the one from the other, so as to make their difference more sensible. The different sorts of colors, generally used in these kinds of drawings, are, Indian-ink, carmine, verd i grease, sap-green, gum-bouge, Pru ian blue, indigo, and umber. Indian-ink is the first and most nece ary thing required in drawing; for it serves, in drawing the lines, to expre hills or rising grounds, and, in short, for all what is called shading in drawings. The best sort of Indian ink is of a bluish black, soft and easily reduced into a liquid, free from sand or gravel. It is made in oblong squares. The manner of liquefying it, is by putting a little clear water into a shell or tea-cup, and rubbing it gently ’till the water is black, and of a consistence much like common ink: when it is used for drawing lines, it must be made very black, though not too thick, otherwise it will not easily flow out of the camel hair pencil; but when it is for shading, it must be pale, so as to go over the same shade several times, which adds a beauty to the shading. Carmine , is an impalpable powder, and the fairest red we know of: it serves for coloring the sections of masonry, the plans of houses, and all kinds of military buildings; as likewise their elevation; but then it is made of a paler color. It is also used for drawing red lines in plans, to represent walls. It is of a high price, but a little will go a great way. It must be mixed with a little gum-water. Verd i grease , or sea-green , used in drawings, is either liquid in small phials, or mixed in little pots or shells, . it serves to color wet ditches, rivers, seas, and in general to represent all watery places; it is most soluble in vinegar; and mixed with vinegar makes a fine green ink. Sap-green , is a stone of a faint yellowish green, when liquefied with clear water: but when mixed with a little sea green, it makes a beautiful gra -green; but, as all mixed colors are liable to fade, if verd i grease can be had, it will be much better. Sap-green is very cheap. Gum-bouge , is a fine yellow gum. It may be di olved in water, but requires no other gum: it serves to color all projects of works; as likewise to distinguish the works unfinished from those that are complete. It serves also to color the trenches of an attack. Indigo , is in small cakes, and very cheap; it serves to color iron, and roofs of buildings which are covered with slates: it must be well ground upon a smooth stone or gla , and mixed with a little gum-water. Pru ian blue , is a kind of friable substance of an exceeding fine blue: it is used to represent the color of blue cloth in drawing encampments, battles, . It must be well ground, and mixed with a little gum-water. Smalt , also a good sort of blue, and may be used for the same purposes. Ultramarine , is an impalpable powder, and of a very delicate sky-blue. It is a color of high price. Umber , is a yellowish brown color in powder: when it is mixed with gum-water, it serves to color dry ditches, sand, and all kinds of earth. By mixing a little red ink with it, it will make a wood color . If some tobacco-leaves be steeped in clear water for several hours, and filtered through a woollen cloth, or brown paper, with a little red ink mixed with it, it will make the best earth or wood color , as lying smoother than any other. Gum-water , is best when it is made some time before it is used; for which purpose take some gum arabic and steep it in clear water for some hours, ’till it is di olved; then strain it through a woollen cloth or brown paper, and preserve it in phials, well stopped, ’till wanted.