The quantity of air allowed to pass is regulated by the extent to which K, Fig. 13, is opened. The water being in E, and this vessel communicating with the atmosphere through the pipe not shown in the Figs., the water falls into the two pipes, and is conducted by one to set the wheel in motion, and by the other to the fountain-jet, through which it issues and again falls into the basin, and thence again into G.
An ingenious and inexpensive timekeeper may be made by any boy for a few pence and a little labour. Buy a sheet of millboard, the thicker the better--size, 27 in. by 22 in.--cut off a strip 10 in. by 27 in., and shape it as shown in Fig. 16, the top part to be 10 in. square, and the lower 17 in. by 4 in. Next mark off the remainder of the millboard into three equal parts of 4 in. each, as shown in Fig. 17, then, with a straightedge and a sharp knife, cut half through the lines AA. This will form the two sides and back of the case. The funnel (B, Fig. 18) should be made of tin, with a square top to fit over the millboard, and have a very small aperture at the point; any tinman will make this for 3_d._ or 4_d._ The spindle (C, Fig. 18) must be 3-3/4 in. long, 3-1/2 in. deep in front, diminishing to 2 in. at back, have a screw-shaped groove from end to end, and work on a small spindle or axle, projecting 1 in. in front, for the hand to be connected to, and 1/2 an inch at rear. If the young horologist has not a lathe at his disposal, the spindle can be obtained from a turner for a few pence. The weight may be made of a piece of shaped stone, or of an empty stone ink-bottle, from the neck of which the cord passes over the bar (C), round the grooves of the spindle, and out of the hole (K). A small weight, such as a bullet, must be fastened to the other end. A piece of canvas should be glued round the edges of the case, and the whole painted with a good coating of Brunswick black, over which any design may be made, either with gold lines, grotesque figures, or coloured pictures. The dial should be of white paper, 7 in. in diameter, and the hand cut out of the spare millboard and then gilded. Four small reels (E, Fig. 17), such as are used for silk, should be glued on the back, to keep the case from the wall, and a ring fastened to the top to hang it by.