401⁄2
5938⁄76
100
No. LXI.—LOOPING THE LOOP
Here is quite a pretty scientific experiment, which any one of a handy turn can construct and arrange:—
The spiral track is formed of two wires bent, and connected by curved cross-pieces. The upper twist is turned so that the ball starts on a horizontal course.
During the accelerated descent the ball acquires momentum enough to keep it on the vertical track, held outwardly against the wires by centrifugal force.
Convenient proportions are: height of spiral two feet, diameter six inches, and wire rails three-quarters of an inch apart.
No. LXII.—A MECHANICAL BIRD
A close approach to an ideal flying machine can be made with a little ingenuity. Two Y-shaped standards, secured to the backbone rod, support two wires which carry wings of thin silk, provided with light stays, and connected at their inner corners with the backbone by threads.
