Imitation leather and black twill joined with thin glue and flour paste are suitable materials for the conical bellows for a camera. The paste should consist of i parts of thin glue to 1 part of flour, the latter rendering the paste less likely to crack. Two thicknesses of twill should be used. Take a piece of leather and a piece of twill, each 1 yd. by 1/2 yd., and join and pin down on a board, inside uppermost, having first well rubbed the board with chalk. Draw a line A 1! in the centre at the bottom, say 7 1/2 in. long, and from the centre of this erect the line C D, and at 18 in. from D draw the line E F parallel to A B, say 4 1/2 in. long, to fit the rising front. Now join the points AE and BE. Now place the blunt point of the compasses at B and with any radius describe an arc of a circle ; then with the point G where the arc cuts B F measure the distance G H, and with the same radius mark off at K and draw a line from B through K 7 1/2 in. long. This gives the angle for the sides. The other sides are marked out in the same manner. The fourth side is divided into two, so that the join may come in the centre of the bottom. An extra piece I, i in. wide, is provided for joining. Now rule a series of lines 1/2n. apart parallel to the base lines.

The folding and creasing lines are thus marked out, the thick lines representing the under and the thin ones the upper lines. A convenient plan for ruling the lines is to fasten the material loosely to the board with a drawing-pin at O. The material may then be swung round at an angle, a T-square being placed parallel in each case to the longer thick line as M, N and so on, or parallel alternately to AB and A P, the other lines being ruled on each side in the same fashion. The diagonal lines are put in with a set-square, so that the angles marked are 45 the other lines being parallel to them. Cut off the surplus, join up, and crease into shape with the fingers. The heavy lines are best put in with the stylus, which will show them on the reverse side in white chalk. It is advisable first to practise the ruling and creasing on some brown paper. Bellows can be purchased ready made very cheaply.

Conical Bellows for Camera.