316 HISTORY OF ASTRONOMY. 



tremely light brass spring, which is secured to a block of 

 ivory or hard wood, and which has no connection with 

 the metallic parts of the clock, rests by its free end on 

 the circumference of the disc. A copper wire is fastened 

 to the fixed end of the spring, and proceeds to one end 

 of the wire of the electro-magnet ; while another wire 

 attached to the clock-frame is continued until it joins the 

 other end of that of the same electro-magnet. A con- 

 stant voltaic battery, consisting of a few elements of very 

 small dimensions, is interposed in any part of the circuit. 

 By this arrangement, the circuit is periodically made and 

 broken, in consequence of the spring resting for tme 

 second on a metal division, and the next second on a 

 wooden division. The circuit may be extended to any 

 length ; and any number of electro-magnetic instruments 

 may be thus brought into sympathetic action with the 

 standard clock. 



In the year 1840, Mr. Alexander Bain, of London, in- 

 vented an arrangement by which it was proposed to work 

 a great number of clocks simultaneously.* The follow- 

 ing is the method by which the regulating clock was 

 made to break the electric circuit. A B is a pendulum 

 vibrating seconds. C is a plate of ivory affixed to the 

 frame of the clock, in the middle of which is inserted 

 a slip of brass D, communicating with the positive pole 

 of a voltaic battery. To the pendulum is attached a very 

 light brass spring E in such a manner that every vibra- 



* Applications of the Electric Fluid to the Useful Arts, *by Mr. 

 Alexander Bain, page 9f. 



