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The pin lift, Fig. 22, page 11, is useful for extracting stubborn pins.

Ink.—The ink used in architectural drawing is a special kind that will not corrode the instruments. It is usually called Indian ink, but is really made in China (that is, the genuine). This requires to be rubbed up in water in a saucer — the bottom of an ordinary tea saucer can be utilised if the proper one is not at hand—it is nibbed up similarly to cake colours.

Only sufficient for use at the time should be mixed, as it dries quickly and becomes gritty if remoistened after drying in the saucer. A little indigo either from the domestic " blue " bag or artists' water-colour mixed in the liquid improves and intensifies the black. Various liquid " Indian " and waterproof inks in bottles are now prepared and stocked by dealers ; these are convenient when much inking in has to be done. They are also useful for drawings that have to be coloured, as this kind of ink will not wash up, but it is rather difficult to use in line pens, as it dries rapidly and clogs the pen, which requires constant cleaning or replacing. The author keeps a phial of water at hand, into which the pen can be dipped occasionally.

Tracing- Paper and Cloth - -This is specially prepared paper or linen which is semi-transparent. When placed over a drawing, the lines, etc., can be seen through it, and easily copied or " traced" with pencil or pen. It is supplied in sheets 20 in. x 30 in. and 30 in. x 40 in., also in rolls of various widths and about 21 yards long.

Scales are instruments of wood, metal, cardboard, etc., having one or more faces, upon which are engraved or printed a number of equal divisions and subdivisions, which may represent yards, feet, inches, etc., as determined. They are used to set off dimensions upon drawings to any desired reduction in size of the original or object represented.

When a drawing is made of the same dimensions as the

20 CONSTRUCTING SCALES

object it represents it is said to be drawn " lull size," when made smaller, it is said to be drawn " to scale." Such a drawing must, if it is to be used again for obtaining accurate measurements of the object, be made proportionately throughout- -that is, every part of it must be drawn to the same scale, and it is to ensure this, in technical drawings, that carefully prepared " scales " are used. The majority of scales are made i foot long ; but, of course, may be of any other length the maker or user chooses, and they may bear from two to a dozen different scales on their faces. For students' drawing purposes, cardboard scales with not more than one scale at each edge are to be preferred, as with these there is less likelihood of mistakes arising through using the wrong scale. It is often necessary to set out a scale upon a drawing, as a suitable one may not be upon the instrument in the possession of the draughtsman, and in important drawings, the scale should always be drawn first upon the paper and worked from, then any alteration in the size of the sheet due to atmospheric conditions will not affect the measurements, as the scale will alter in the same ratio as the drawing, whilst an 'independent scale might not.

On page 21 are shown five different scales suitable for laying down on drawings and as many different ways of drawing them; these details differ with the taste of the draughtsman. Fig. 1 is a scale of | in. to the foot, and is made long enough to measure 12 feet. Anything drawn to this scale would be of the real size of the object represented, because there are forty-eight quarter inches in a foot, and is called the representative fraction of the scale, or, shortly, "the fraction."

Fig. 2 is a scale of J- in. to a foot; the fraction being f\.

Fig. 3 is \ in. to the foot, the fraction being -/f. Fig. 4 is 1J in. to the foot or I the real size ; because there arc eight one and a half inches in a foot, and as the representative fraction of this scale is -J, care must be taken when reading instructions not to confuse it with i inch to a foot. This

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