634 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



explain to us all the ingredients requisite for this new application of 

 electro-magnetism. We will describe first the electric regulators. 



There are two distinct parts in an apparatus of this sort, as 

 indeed there are in every telegraphic apparatus. There is first the 

 mechanism connected with the regulating clock for transmitting and 

 interrupting periodically, and at equal intervals, the current from a 

 battery, or some other electromotor. This current communicates the 

 motion to the receiving apparatus, that is, to the mechanism for 

 moving the hand on each dial. This is the indicator. 



Take for example Garnier's regulator. 



The regulating clock is an ordinary one, and the following is the 



FIG. 414. Garnier's electric regulator : 

 transmitting apparatus. 



FIG. 415. Indicator of Garnier's electric 

 regulator. 



simple way by which, when in motion, it successively transmits and 

 stops the ciirrent in the circuit. The dial-wheel of the clock carries 

 on its axis a wheel with four cam-shaped teeth. The rotation of the 

 wheel first raises the hook d of the lever /, and then lets it fall. In 

 "the first case, that represented in Fig. 414, the two poles -t- and of the 

 battery are in communication by the contact of the two metallic levers 

 t and / ; the circuit is closed and the current passes. In the interval 

 of the passage from one tooth to another, the lever / falls, contact 

 ceases, the circuit is opened, and the current is interrupted. The 

 contacts of the two pieces are made of gold, or of an alloy of gold 

 and platinum, in order to avoid oxidization, which would stop the 



