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THE POPULAR SCIENCE MONTHLY. 



THE ELECTRICAL. POLYSCOPE. 



THE electrical polyscope is .a simple and ingenious apparatus for 

 giving light in the cavities of the human body, the invention of 

 M. Trouve, who has distinguished himself by the contrivance of sev- 

 eral other instruments useful to physicians and involving curious ap- 

 plications of electricity. It consists of an energetic and constant bat- 

 tery, of a reservoir or secondary battery, and of parabolic reflectors 

 adapted to the different uses to which it may be applied, which are 

 furnished with additional mirrors or used without them. A minute 

 platinum thread, connected with the conducting wires of the battery, 

 is placed in the middle of each reflector. When the battery is put in 

 action, the wire becomes incandescent. A special rheostat is provided 

 to regulate the flow of the electricity, which plays a part similar to 

 that of the faucet of a water-reservoir, and controls the flow of the 

 fluid with such exactness as to permit the finest threads of platinum 



Fig. 1. 



Fig. 2. 



to approach the point of fusion without passing it. The melting-point 

 of the wires used having been determined in the beginning, can al- 

 ways afterward be avoided without trouble. A galvanometer with 

 two circuits, in which the electro-motive force of the reservoir and 

 that of the battery are in opposition, enables the operator to observe 



