Page:Popular Science Monthly Volume 88.djvu/376

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��Popular Science Monthly

���To photograph a spark like this is no feat of simple "snap-shot" work. It takes some preparation, but it can be done by any care- ful experimenter

How to Photograph Electrical Sparks

THE following experiments can be performed with a Vi'" spark-coil. The ordinary photographic plate is used in all cases, its size depending on the oljjects. The experiment is conducted in a darkroom or in a room lighted only with a ruby photographic lamp. Any white light will spoil the plates instantly. After exposing the plates they must be developed.

Take a small bottle with a wide mouth and fill it half full of any talcum powder. Over the mouth place a thin piece of gauze to act as a fine sieve. Tie the gauze around the neck of the bottle with a fine string. Place the photo- graphic plate on a metal plate with the coated side up. Connect the metal plate with one of the secondary posts of the spark-coil. Sift a thin layer of the talcum powder over the photographic plate. Now place a very fine metal point in the middle of the plate (a pin is excellent). Connect the pin with the other post of the coil and make one spark, lasting one second or less. Wipe off the powder and the plate is ready for developing.

��Trimming Veneered Edges by Electricity

IT has been the custom to trim the edges of veneered work with a draw- shave or rasp, but this is always accom- panied by danger of injury to the work. The importance of having veneered work perfect has prompted a manufacturer to bring out an electric-trimming device, which makes injury to the work im- possible.

Built within an aluminum case, which protects the saw on all sides except the cutting edge, is an electric motor. This drives the special saw for trimming the veneered edge at very high speed and makes possible the perfect removal of the delicate wood and the glue as well. The saw is adjustable to any height by means of a screw, so that the veneer may be removed flush with the work or the edge extending to any desired height. Power is supplied from a lamp-socket.

���A boy can operate this electric planer (for it is nothing else). The concentrated power of electricity makes perfection easily attainable by the modern workman

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