362 



SEC. 11. ASTRONOMY. 



repelled by the magnets, thereby giving motion to, and maintaining the vibra- 

 tion of, the pendulum. The connexions between the batteries and motor and 

 sympathetic clock pendulums with the position of magnets are shown in 

 .Fig. A. 



3rd. The sympathetic pendulum is also made with an "ordinary ball or bob, 

 carrying a single magnet bar passing into small coils of wire fixed to the case 

 and placed in circuit with motor clock, as shown in the square case. 



4th. To admit of a pendulum vibrating in seconds being introduced within 

 the limits of the usual office round clock-case, two small coils, one below and 

 the other above the point of suspension, are used, having double magnets 

 placed for each coil, through both of which the currents from the motor clock 

 are passed. 



This form of pendulum requires a more powerful battery to sustain its 

 motion, and has less momentum than the long pendulums. Its construction 

 is shown in the circular case, and in Fig. B. 



5th. An arrangement to enable a pendulum vibrating in half seconds to 

 beat seconds is shown in Fig. C. 



