APPLICATION OF THE ELECTRIC TELEGRAPH. 317 



tion of the pendulum brings the free end of the spring 



into contact with the strip of brass D, thus completing 



the electric circuit through the 



upper part of the pendulum to the 



negative pole of the battery ; while 



the circuit is broken as soon as the 



spring touches the ivory. 



Subsequently Mr. Bain adopted 

 the arrangement of closing and 

 breaking the circuit by means of a 

 short brass bar, placed in a horiz- 

 ontal position near the middle of 

 the pendulum; the bar being slid 

 back and forth about one inch at 

 each vibration of the pendulum. 



In 1844, Mr. Joseph Saxton 

 proposed to break the electric 

 circuit by a pin on the pendulum rod striking a small 

 tilt hammer, and also making the circuit by a lancet- 

 shaped point of platinum at the bottom of the rod 

 passing through a globule of mercury. Early in 1846, 

 he proposed both methods again, when objections were 

 made against them on the supposition that the current of 

 electricity passing through the pendulum rod might affect 

 the rate of the clock. To meet this objection, he pro- 

 posed to insulate the pin by a piece of ivory, or use a 

 glass pin. Or if the other method was used, instead of 

 passing the current through the rod, he proposed to at- 

 tach at the top of the rod a small lever to be raised by 



