THE ELECTRIC TELEGKAPH. 



It is evident that during each revolution of the wheel there will 

 be as many pulsations of the current as there are teeth, and since 

 the rotation of the wheel may be as rapid as may be desired, and 

 the teeth as numerous, there is no practical limit to the possible 

 rapidity of these pulsations. 



133. Another contrivance, by which pulsations are imparted to 

 the current, consists of a metallic wheel around the face of which 

 a sinuous groove is cut, in which a pin, projecting from the arm 

 of a metallic lever is inserted, so that when the wheel is turned 

 upon its axis, the pin attached to the lever receives from the 

 sinuosities of the groove a motion alternately right and left, which 

 is imparted to the other arm of the lever. This latter arm plays 

 between two metallic stops, one of which is connected with the wire 

 w, along which the current flows. When the arm of the lever 

 comes in contact with it, the current is transmitted on the lever 

 to the sinuous groove of the wheel, and from thence to the line- 

 wire w'. When the lever oscillates to the other side, the contact 

 with the wire w is broken, and the current is interrupted. 



This will be more clearly understood by reference to the fig. 51, 

 where A B is the wheel, c c c the sinuous groove, G o H the lever 



playing on the axis o. From 

 G, a short projecting piece, 

 G G', passes in front of the 

 wheel across the groove, and 

 from this piece a pin projects, 

 which enters the groove. The 

 arm H plays between two 

 stops, P and r', provided with 

 springs to ensure the contact 

 with the lever. The stop P 

 is connected with the con- 

 ducting wire w, and the groove 

 c is connected with the wire 

 w'. "When the wheel is turned, 

 the pin at G' is driven by the 

 sinuosities of the groove alter 

 nately right and left, by which 

 a corresponding motion is imparted to the arm H of the lever, so 

 that its end is driven alternately against the stops P and P'. 

 When it is thrown against P it is in metallic connection with the 

 wire w. When it is thrown against P' that connection is broken. 

 Now, if a current flow along P, it will pass to the lever when H 

 falls against P, and will pass by the lever and the groove c c to the 

 wire w'. When the arm n is thrown against r', the contact with 

 p being broken, the current is suspended. Thus, as the lever is 

 190 



