264 SCIENTIFIC RECREATIONS. 



The uses to which the electro- motograph may be applied are various. 

 It can produce mechanical motion even at a distance, and is useful to lessen 

 friction by machinery ; and in this way its service to railways and other 

 locomotive systems may be estimated. It is a great help to telegraphy 

 by increasing the speed of transmission, and can ascertain the beatings of 

 the heart of the apparently dead. It amplifies sound in a much greater 

 'degree than the microphone, by which even a fly can be heard moving. In 

 fact, the limit of the usefulness of this wonderful machine has not been 

 reached. 



Another very ingenious apparatus has been developed by Professor 

 Bell. This is for the purpose of ascertaining the position of bullets in the 

 body. The following is condensed from the Times : 



" Two conductors are used, and the ball completes the circuit. 

 Professor Bell inserts a fine needle in the suspected region. It is con- 

 nected by wire with one of the binding screws of a telephone, which the 

 surgeon holds to his ear ; the other binding screw being connected with a 

 metallic mass applied to the skin. When the needle point touches the ball, 

 an electric couple is formed, and the current generates the sound in the 

 telephone. The surgeon may then use his knife with confidence, guided by 

 the needle. He may make several insertions of the needle if necessary 

 without danger, and any pain may be obviated by etherization. This 

 simple method (which should prove useful on the field of battle) was tried 

 with success with a lead ball introduced into a piece of beef. Contact of 

 the needle with bone had no effect, but a very distinct sound was heard 

 each time the ball was reached. A modification consists in inserting a 

 vibrator in the circuit ; this gives a musical note in the telephone at each 

 contact of ball and needle. Again, if the circuit include a battery, the 

 telephone sounds may be heard by several persons at once. A sound is 

 heard, in this case, whenever the needle enters the skin ; but, on reaching 

 the ball, it is much intensified, owing to lessened resistance. A galvano- 

 meter may be used in place of the telephone." 



Mr. C. Vernon Boys has exhibited and described a very ingenious new 

 integrating machine of his invention, and its application as a measurer of the 

 electric energy in the circuit of an electric lamp or a dynamo-electric motor. 

 Mr. Boys' mechanical integrator belongs to the class termed tangent machines, 

 and consists essentially of a small disc or wheel running along the surface of 

 a drum or cylinder. When the wheel runs straight along the drum parallel 

 to its axis there is no rotation of the latter, but when the wheel is inclined 

 to the axis the drum rotates, and the integral is represented by the amount 

 of rotation. Continuous action is secured in giving the drum a recipro- 

 cating motion along its axis, so that when the wheel has travelled to one end 

 of the cylinder it can travel back again. The new integrator is especially 

 adapted for measuring forces which are either delicate or variable. It is 

 applied by causing the varying force to be measured to vary in a correspond- 

 ing manner the inclination of the wheel to the axis of the rotating cylinder. 



