Page:The American Boy's Handy Book edition 1.djvu/396

will allow the disks to revolve freely. Attach a string to the stick J at a point that will come opposite the string-hole in the side of the handle, when the stick J is slid into the hole at the top of the handle K. The wooden disk is made to spin exactly in the same manner that motion is imparted to the potato mill already described. When in motion the colors on the paper disks will blend and produce, with each change of position, a number of beautiful variations. The two paper disks blend together, making a large circle three and one-half inches in diameter, composed of concentric rings of the most lovely hues―red, pink, purple, green, and all the different shades and combinations imaginable are portrayed with ever-changing variety by the spinning rainbow whirligig.

is a very ingenious toy, consisting of a circle of white card-board, upon the surface of which any number of black rings are painted, one within the other, until it resembles an archery butt or target.

The disk is tacked or glued securely to a stick or handle (Fig. 230) so that it is impossible for it to really revolve, yet if you grasp the toy by the handle and give your arm a motion similar to that of the shaft of an engine, the disk upon the stick will appear to revolve like a wheel, and so closely does the optical delusion resemble actual motion that it will deceive almost any one who is not familiar with the experiment.