eel pin fitted to a plate on the base. A carriage travels along
the jib, being kept at the required distance by a cord passing over a
wheel at the end of the jib. A cord attached to the carriage passes over
a pulley connected with the weight, and also over the wheel of the
carriage, to the wheel directing it to the axle, which is turned by a
cog-wheel and pinion taken from an old clock.

The carrier of the elevator shown in Figure 12 is hoisted by a cord
passing over a small iron pulley fixed to the cross-beam of the grooved
posts, and thence to the spool, or axle turned by a crank.

A clock-spring attached to a square wooden rosette is shown by Figure
13.

Figure 14 represents a pump improvised by John B. Cartwright from an old
mincing-machine.

A handle turns a series of spur-wheels, which in turn give a rapid
motion to a twelve-inch walking-beam. To one end of this walking-beam is
attached a piston-rod, with a soft rubber disk working in a brass
cylinder five inches long and three and a half inches in diameter. Iron
fittings, including two brass valves, one on each side, connect with the
cylinder; an air-chamber is formed with a fitting and cap. The suction
caused by the upward motion of the piston will draw water from a pail or
cup through a rubber tube connected with the end fitting of the
right-hand valve, then through the valve to the cylinder; the downward
motion of the piston causes the water to pass through the left-hand
valve to the receiving vessel, and the air-chamber tends to make the
flow regular. Parts of the machine were painted blue and striped with
gold bronze.

[Illustration: SIMPLE MECHANICAL APPARATUS MADE BY BOYS UNDER FOURTEEN
YEARS OF AGE.--DRAWN BY J. ABDON DONNEGAN.

Fig. 8 A DUMB WAITER

Fig. 9. GUILLOTINE

Fig. 10. A DERRICK

Fig. 11. FOUNDRY CRANE

Fig. 12. BRICK & MORTAR ELEVATOR

Fig. 13. CLOCK SPRING

Fig. 14. FORCE PUMP

Fig. 15. SIMPLE SUN MAGIC LANTERN OR HELIOSTAT.

Fig. 15.A.

Fig. 16. ARC ELECTRIC LAMP]

By the removal of one pane of glass from a window facing south, the
apparatus shown in Figure 15 may be used, like a magic lantern, to
project transparencies, in a darkened room.

A pine board, fourteen inches square and one inch in thickness, has an
opening in the middle to receive a wooden frame seven inches square,
holding a six-inch cosmorama lens, having a focus of eighteen inches. A
three-inch plano-convex lens having a focus of nine inches, mounted in