[Illustration:  Chinese Doing the Grand Whirl]

with their arms locked about each other and the two outside persons swinging in midair with their bodies almost horizontal.

** Home-Made Photograph of a Lightning Flash [176]

How many times has each amateur photographer tried to photograph the lightning’s flash?  Some good pictures have been obtained by a ceaseless effort on the part of the operator.  Here is a method by which you can make a picture of a streak of lightning on a clear night in your own house.  Paste two strips of black paper on a piece of glass that is 10 in. square so as to leave a clear space through the center 2-in. or more in width.  Smoke this uncovered space over a candle’s flame until the soot is thick enough to prevent light passing through.  Take a sharp lead pencil and outline a flash of lightning upon the smoked surface, using a fine needle to make the smaller lines, and then set the glass up against the back of two boxes which are set to have a space between them of 4 or 5 in.

A lighted candle is held behind the glass so the light will shine through for focusing the camera.  After darkening the room set your camera ready for the exposure and burn a small quantity of flash light powder in the same place in which the candle was held.  This will make an impression upon the plate of the flash drawn on the smoked glass.

[Illustration:  Lightning Flash]

** How to Make a Static Machine [177]

Static electricity is produced by revolving glass plates upon which a number of sectors are cemented; these sectors, passing through neutralizing brushes, distribute electric charges

[Illustration:  Details of a Homemade Static Machine]

to collecting combs attached to discharging rods.  The glass selected for the plates must be clear white glass, free from wrinkles, and of a uniform thickness.  Two plates are necessary to make this machine, and the glass should be of sufficient size to cut a circular plate 16-in. in diameter.  A hole must be made exactly in the center of each plate, and this should be done before cutting the circle.  One of the best ways to make the hole is to drill the glass with a very hard-tempered drill, the cutting edge of which should be kept moistened with 2 parts turpentine and 1 part sweet oil while drilling.  The hole is to be made 3/4 in. in diameter.  The circle is then marked on each plate and cut with a glass cutter.  The plates are trued up, after they are mounted, by holding a piece of emery wheel to the edges while they are turning.  Water should be applied to the edges while doing the work.

The sectors are cut from tinfoil, 1-1/2 in. wide at one end, 3/4 in. at the other, and 4 in. long.  A thin coat of shellac varnish is applied to both sides of the plates, and 16 sectors put on one side of each plate, as shown in Fig. 1.  The divisions can be marked on the opposite side of the plate and a circle drawn as a guide to place the sectors at proper intervals.