922 



Popular Science Monthly 



handling. The electric type of operator, 

 although a little more bulky, gives real 

 satisfaction and is very simple. 



The illustrations plainly show the opera- 

 tion of the device. The agitator proper 

 consists of two magnets similar to those 

 used in a call-bell. These when energized 

 attract the armature above them attached 

 to a long rod, which is attached to the 

 shutter lever by a small wire hook movable 

 on it so as to follow the camera front when 

 focusing. The small weight on the rod is to 

 steady the movement and to allow the 

 magnets to operate on less current, being 

 thus assisted by gravity. The windings 

 from the coils are led to two small brass 

 screws in the side of the base, and it is to 

 these that the spring clips on the cable ends 

 are fastened. The small clamp holds the 

 apparatus to the camera bed without 

 altering its action in any way and may be 

 removed instantly when the camera is 

 wanted for other work. No dimensions are 

 given, as the instrument must be built to 

 fit the camera for which it is intended. 



FOR WIRES TO PUSH-BUTTON^ 



BATTEPY 



Dimensions for the wire carrier and battery, 

 and the wiring diagram for the connections 



The flexible lamp-cord used as cable is 

 wound on a wooden reel which also holds 

 the batteries. The core of the reel con- 

 sists of two wooden end pieces connecting 

 the flanges. The two double-cell flash- 

 light batteries are slipped between the up- 

 per and lower pieces of the frame where 

 they make contact with "the spring brass 

 clip fastened on the inside of the end piece. 

 The wiring diagram shows the connection 

 with the push button and camera. 



The entire outfit, including plate-holders 

 and other paraphernalia needed, may be 

 fitted into a small rattan suit-case. The 

 tripod legs when folded may be strapped to 

 the outside of it. The only other requisite 

 is an unlimited supply of patience, but as 

 something of interest is always in progress 

 in the woods and fields the time thus spent 

 is by no means void. — C. Breder, Jr. 



Troubles with the Safety Spark- 

 Gap on Motorcycles 



THE owner of a single cylinder motor- 

 cycle equipped with a well known 

 make of high tension magneto, experienced 

 some trouble with it which he attributed 



Most high tension magnetos are provided 

 with a safety spark-gap to prevent damage 



to weak magnets. He accordingly took ofT 

 the magnets and had them recharged. Upon 

 replacing them he found the performance 

 of the magneto to be worse than before. 

 He then dismantled the magneto to look 

 for further trouble in the armature and 

 found what he thought at the time was 

 the cause of all the trouble. As is well 

 known most high tension magnetos are pro- 

 vided with a safety spark-gap, the purpose 

 of which is to provide a path to ground for 

 the high tension current generated in the 

 armature, and thereby prevent damage to 

 the insulation, in case the spark plug wire 

 becomes disconnected or the gap in the 

 spark plug is too great. These safety spark- 

 gaps are arranged in various forms and in 

 this particular type is arranged as shown 

 in the accompanying illustrations. 



The safety spark-gap back of the col- 

 lector ring is clearly shown in the illustra- 

 tion. In the diagram the armature winding 



TO 

 INTtRRUPTER 



'SAFETY 5PARK GAP 



A diagram of the armature winding to show 

 how the safety spark-gap should be connected 



in which the safety spark-gap is located is 

 also indicated. 



Anyone not experienced in the construe- 



