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in common use amongst draughtsmen for the same purpose. They are made in the form of a large square pencil, with rubber inserted in the body of it. To use it the wood is cut away, as is done in pointing an ordinary pencil, exposing the rubber, and it is then applied to the pencilled line with a to-and-fro motion of the hand, pressing lightly, until the line disappears. Fig. C Ink. A further and all-important requisite to the student draughts- man is ink with which to line in his drawings after they have been carefully put in in pencil. We say this is an " important " requisite, because so much depends on its quality. It is generally known as India or China ink. The definition given of it in standard dictionaries viz., "a substance made of lampblack and animal glue" is no doubt answerable for the large amount of a material made and sold in Britain under its name. Pure India or China ink is only made in those countries, because the special wood from which it is produced is found only in those regions; therefore in purchasing ink for use en 8 FIRST PRINCIPLES OF drawings, the only way to ensure its being the real article is to obtain it from a bond fde importer. The best mathematical instrument- makers are generally importers of it. It is sold in hexagonal sticks, as shown in Fig. C, and is expensive, but small oval and round sticks of it are to be had costing about a shilling each. 6. Before noticing the few "instruments" that are necessary when commencing the study of mechanical drawing, we think it advisable to show, in a combined sketch (Fig. D), the special tools viz., drawing-