The driving rod, shown at the right of the larger sketch, is ¹⁄₈ in. in diameter and 9¹⁄₂ in. long. The flattened portions near the upper end are drilled to receive the ends of the cords which wind and unwind on the shaft at the top of the handles. A brace of similar wire is fixed near the middle of the handles so that they pivot on its ends when the lower ends of the handles are pressed together, as shown in the sketch at the right. The handles are of wood, ¹⁄₄ in. thick, ¹⁄₂ in. wide, an 6¹⁄₂ in. long. Their ends are rounded and slight notches are cut into the corners near the ends, to provide for the tying of the cords.
A wide rubber band, slipped over the handles near their upper ends, causes them to close at the top, and when the fan is in use this will reverse the rotation of the fan. It is necessary only to squeeze the handles inward, and the reverse action is repeated.
Photographing Electric Sparks
Electric sparks may be photographed with simple equipment, and the process offers a diversion from the common subjects for photography. The materials necessary are a spark coil and current source, a photographic plate, facilities for developing it, and a sheet of tin foil. The illustration shows a typical photograph of an electric spark, and the variety possible is unlimited.
The process, which must be performed in a dark room with a ruby light, is as follows: Over the mouth of a small glass bottle, partly filled with talcum powder, tie a piece of cheesecloth, to act as a sieve. Arrange the material on a table, the sheet of tin foil lying flat, and a photographic plate on top of it, coated side upward.
Spread a thin layer of the powder on the plate, through the sieve. Attach a needle to an electric wire and fix the other end of the wire to one of the secondary posts of the spark coil. Attach a second wire to the other post of the spark coil and to the sheet of tin foil. Care must be taken in handling the needle that only the insulated portion, where it is joined to the wire, comes in contact with the fingers, or a shock may result. Place the point of the needle near the middle of the plate and turn on the current, permitting it to produce a spark of not more than one second’s duration. If the exposure is longer than that the result will not be satisfactory. Wipe off the powder and develop the plate. If care has been taken in the process, a photograph similar to the one shown in the illustration will result.
¶Shoulder hooks fixed about a shop, so that handsaws may be placed on them by the handle, will save damage to saws.
Cannon-Shell Dinner Bell
Being called to dinner by the stirring peal of a bell made of a cannon shell is a novelty in use in Toronto. The bell shown in the sketch was made of a 3-in. brass shell, and when struck with a gavel gives out tones that penetrate throughout a large house.