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C. Barus — Simple Chronograph Pendulum. 



Art. LY. — A Simple Chronograph Pendulum ; 

 by C. Barus. 



To give time to the chronograph, a break-circuit chronometer 

 or a seconds clock is usually employed. Frequently, however, 

 one is not in possession of this elaborate apparatus, or it is not 

 expedient to make use of it. The following simple mechan- 

 ism by which an ordinary seconds pendulum is both kept in 

 motion and made to record its oscillations on- one or more chro- 

 nographs sharply, may therefore merit description. 



Figure 1 gives a sectional elevation of 

 the device, figure 2 a side view with elec- 

 tric parts omitted. A is the seconds pen- 

 dulum consisting of a light wooden rod (A) 

 joining the heavy metallic bob C and the 

 knife edge c. The latter is supported 

 by the metallic plates a, and these and the 

 bob are electrically connected. The top of 

 the pendulum is surmounted by a soft iron 

 armature o, actuated by the electromagnet 

 m in the way presently to be described. 



B is a longer and very much lighter 

 pendulum, consisting of a flat bob n joined 

 (bifilarly) by two very thin metallic wires 

 (B, B) to the adjustable suspension ff. 

 The bob n is prevented from oscillating 

 toward the right by a rigid post e. A 

 ribbon of platinum d is wrapped around 

 the bob C and a quadrantal spring g of 

 thin platinum foil projects from the bob 

 n for the purpose of securing reliable electric contacts. The 

 bob n consists of two small square parallel plates, between 

 which the wires B B and the platinum strip g are clutched by 

 a single central screw. 



Current is obtained from batteries at E (two or more Le- 

 clanche cells) and circulates when the circuit is closed as 

 shown by the arrows. P, P', etc., are the chronographs to 

 which time is to be given, these and the electromagnet m 

 being joined in multiple arc. 



The mode of action is easily intelligible. Whenever the cir- 

 cuit is closed by the bobs at g d a current passes through m y 

 P, P', etc. 



Suppose the post e and the strip g to be removed, and the 

 bobs n and C to be in inelastic contact. Then on moving A 

 to the left, this pendulum will push the pendulum B in front 



