348 



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 

 witli 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 



