Page:The American Boy's Handy Book edition 1.djvu/397

A picture of a wagon, with wheels made like the disks of the paradoxical whirligig, may be made, and the wheels will have all the appearance of revolving when a wabbling motion is imparted to the picture. There are many curious experiments that can be tried in this line―spirals may be made to twist around; pictured machinery may be given the appearance of actual moving wheels, etc. The philosophy of all this is best explained in the description of the next whirligig.

The phantasmoscope, or magic wheel, is comparatively simple, consisting, as may be seen by the accompanying illustration, of a disk of any diameter revolving upon a pin in the centre. Figures in different poses of arrested action are painted or pasted upon the one side; under each figure is an oblong opening or slot. Much amusement can be derived from this old and simple toy. We herewith give one with the correct positions of a horse trotting a 2:40 gait, drawn in silhouette upon the outer margin of the wheel.

Make a careful tracing of the illustration (Fig. 231) with a lead-pencil upon tracing-paper; reverse the tracing-paper upon a piece of card-board so that the side with the pencil-markings on it will be next to the card-board; after which fasten both card-board and paper to a drawing-board or table-top with tacks, so that neither tracing nor card-board can slip. With the point of a hard pencil, a slate-pencil or any similar instrument, go carefully over each line of the tracing as seen through the tracing-paper; be careful not to omit a single mark; it is very provoking to discover, after removing the tracing-paper, that part of the drawing is wanting; but if you have been careful, when the tacks are removed you will find the picture neatly transferred on the card-board. Go carefully over each line on the