APPLICATION OF THE ELECTKIC TELEGRAPH. 321 



lowest point, caused the lever to strike a dot on the tape 

 at the first quarter second, and afterwards at each, half 

 second to the end of the tape. This pendulum had no 

 maintaining power, except its own gravity, as it was only 

 required to act for a few seconds. Electricity was not 

 used in this experiment ; but this machine was the germ 

 of the contrivances described on page 318 for breaking 

 the electric circuit. 



In the year 1847, Mr. J. J. Speed, of Detroit, Michigan, 

 conceived a plan for causing all the clocks of a large city 

 to indicate the same time. He proposed to have all the 

 clocks in the city connected with galvanic circuits, and 

 operated from soi^e central battery, the hands on the 

 clocks moving only at given intervals, and at the instant 

 the circuit should be closed. To close and break the 

 circuit, he had a clock constructed with a tilt-hammer, 

 which was lifted by a projecting tooth on one of the 

 wheels of the clock. The credit of this part of the in- 

 vention is conceded, however, to Mr. C. F. Johnson, of 

 Owego, N. Y., and was patented by him in 1846. The 

 idea of applying the galvanic circuit to give motion to 

 house clocks by means of the tilt hammer, is claimed by 

 Mr. Speed. Has attention being soon afterward directed 

 to other objects, Mr. Speed never carried his plan irto 

 execution, and the clock which he ordered to be con- 

 structed with the tilt-hammer arrangement is now the 

 property of the United States Coast Survey. 



Dr. Locke, of Cincinnati, in the autumn of 1848, in- 

 vented an arrangement for breaking the electric circuit 



14* 



