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baize, a coarse kind of open cloth, to keep the steel free from rust. This box is screwed to the side of an office bookcase, and is air-tight. Steel straight edges are more to be relied upon than wooden ones, even when an ebony edge is attached to the latter. In plotting, a flat ivory or boxwood scale is laid upon the paper exactly parallel (see fig. 1) to the base line, and is kept in position by flat weights resting upon its outer edge. A short rectangular flat scale rests upon its inner edge from which to measure the offsets. These offsets are marked on the paper by pricking with a needle point (see fig. 14, p. 101) opposite the proper graduations on one of its edges, the chain distances at which they are measured on the base line being taken off the long scale. Care must be taken that the edges of the offset scale are truly perpendicular to each other, and that the zero on the offset scale slides exactly over the base line. The advantage of using a split offset scale, or one with zero in the centre, is explained in fig. 1. Metal weights require covering, either of baize or leather, otherwise they cover the drawing with marks which cannot easily be removed (see pages 92-94).


Verner's Wrist Plane Table (or Cavalry Field Sketching Board)-7 in. x 5 in., with patent rollers, and strap to fasten on wrist, scale of 1 in., 4 in., and 6 in. = 1 mile in yards; normal scale of H. E. for 20 ft. at 6 in. = I mile; self-clamping Clinometer and 1-in. bar needle Compass,

with direction line, and divided each 10 deg. on ring; complete with ruler and rubber bands, is a useful help in military surveying.

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Enclosures are frequently covered with parallel lines in light ink by a process termed hatching. To assist in drawing these lines, an ingenious arrangement suggested by Harden, consisting of a set square and straight edge, has been employed, connected together in a special manner. The distance is adjusted by stops, one formed by the stud on the scale plate fitting the slot in the set square, the other is a projection on the straight edge, the distance between the two being regulated by the scale plate. The straight edge and set square are moved alternately, each guided by the other, drawing a line at each alternate movement. The practical draughtsman would, however, prefer to estimate his own distances, ruling in the parallel section lines off the edge of one set square which slides along the edge of another set square, the latter being maintained firmly in a set position. In the application of Harden's method to cylindrical shading the straight edge has a projecting arm working between a stationary stud and an eccentric stop as part of the set square. The eccentric and scale govern the distance between the lines drawn, limiting the motion of the between the stops. The eccentric is revolved equal dis


tances according to the scale of degrees, this giving an increasing distance between the lines drawn.

Corey and Barczinsky's Technical Drawing Apparatus consists of a T square (42 inch 32 inch) with two stocks, one of which is fixed, and the other movable. The blade of the T square has two inverted T grooves, in which slides the dial. This dial which is made of brass is graduated into halfdegrees, and is fitted with an indicator and arm, or ruler, also of brass (these latter in one piece, and so arranged that when the indicator shows a certain angle, the ruler forms that angle with a perpendicular to the edge of the T square), at the important angles, viz.: 30°, 45°, 60°, 6710 and 90°. There are special divisions near the edge into which a small knife fitted to the indicator drops and fixes it firmly, the degrees being read through an aperture in the end of the indicator. A small screw lifts the knife out of the division when the angle is wanted to be altered This instrument is a combination of T square, set square of all angles, and protractor; and besides doing the work of each and all of these, it will divide circles or parts of circles into any number of equal parts without calculation. The instrument can be applied to the drawing board by loosening the movable stock, pressing it tightly to the edges of the board and screwing up, when it will travel easily up and down, and thus all horizontal lines are made. The dial slides from side to side in its grooves, and therefore by these two movements it may be placed in any position on the surface of the board, consequently lines either vertical, horizontal, or at any angle, may be drawn. To use the instrument as a set square of any of the common angles such as 30°, 45°, 60°, 6710 and 90°, the knife is raised out of the divisions on the edge by the small screw, and the indicator is moved over the dial until the angle required is seen through the aperture; then by releasing the screw, the indicator will be fixed at that degree.

Such instruments display skill in their construction, but are seldom near to hand in an office when required as they are seldom used, and the remarks made upon page 103 apply thereto.



THE accompanying specimens of typographical hieroglyphics may serve to guide the student as regards conventional signs. (See pages 114-119.) The writing upon a plan should be disposed in parallel directions reading from west to east, or south to north, with the exception of the names of rivers, canals, chains of mountains, etc., which should be adapted to their natural sinuosities. Dotting pens, or pens fitted with wheels for drawing in lines representing boundaries that may be walked over, do not work sufficiently regular in their action to produce neat work. With practice, the draughtsman can speedily draw a dotted line neatly.

Major E. R. James, R.E., in his remarks upon hill sketching, published in "Ordnance Maps: the Methods and Processes Adopted for their Production," states that, "to give pictorial effect and softness of expression to a sketch, the penmanship requires skill in various minor points, which can be acquired by practice only. These are the graduation in the thickness of the stroke in the expression of slopes of gradually varying altitude; the evenness or raggedness of the edges of the strokes; and the manner of disposing the breaks between the ends of the touches. The latter point especially requires great attention, and the breaks between strokes should never form continuous white lines, which attract the eye. Again,

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if the strokes be long and even and the curves gradual, the ground represented is of a smooth surface; if the contrary, of a rough surface. Rocky features being expressed by vertical strokes, the roughness of appearance is materially aided by their introduction. The light is supposed to fall vertically, that is, slopes of like altitude and inclination are similarly expressed, whatever may be their compass bearings."

In order that colour may flow easily, and cover a surface evenly, it is necessary that it should be thin for tinting, as the draughtsman must remember he has not to paint. It is always easy to wash it over again if it is not dark enough, but it is very difficult to wash off the colour if it be too dark.

Wherever it is possible, use a large brush in preference to a smaller one, as you will by this means be more likely to succeed in getting a flat wash, whilst a small brush might make the tint lie in streaks, as it will not complete the surface to be tinted with sufficient rapidity to obtain a flat wash. Care is, however, necessary in using a large brush, so that you may not pass over the outlines. Take care to prepare an ample quantity of the correct tint, and when you have rubbed as much colour as you think you are likely to want, do not at once put the cake back into its place in the box, but stand it on one of its edges so as to allow it to dry, otherwise it will stick to the box.

Blue, red, and yellow are called the three primary colours. When two primaries are mixed they produce a secondary colour. Thus :

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When you wish to mix a secondary colour, such as green, from the two primaries blue and yellow, rub the blue in one division of the slab, and the yellow in another, leaving a space between them. Then, with your brush, mix the two colours in this vacant space; but on no account rub either of the cakes in the colour obtained from the other, as this

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