334 THE POPULAR SCIENCE MONTHLY. 



The actual interval during which the Greenwich as well as the pro- 

 vincial wires on which the time-signal is distributed are kept in circuit 

 being only twenty seconds, the chance of interruption from contact 

 currents is reduced to a minimum. 



The batteries in use are large Leclanche cells, and the power is 

 distributed as follows : 



Copper or " time " Zinc or " preliminary " 

 battery. battery. 



Long lines 80 cells. 60 cells. 



Medium lines 60 " 45 " 



Short lines 40 " 30 " 



Metropolitan lines 40 " . . " 



The Greenwich signal, thus distributed by the chronopher, goes to 

 all parts of the kingdom, and affects receiving instruments provided 

 for the purpose. These are of various kinds ; ordinary telegraphic 

 sounders, electric bells, and galvanometers have been used with suc- 

 cess to note the arrival of the signal. The current has also been made 

 to drop time-balls on the tops of buildings, to expose a model time- 

 ball to view, and to fire guns. 



To test the accuracy of the signals, experiment has been made by 

 returning a wire to Greenwich from the chronopher, and comparing 

 the signal received on this wire with the signal sent from the observ- 

 atory ; no difference could be perceived between the indications of 

 two galvanometers placed side hy side showing the passage of both 

 currents. The signals were thus shown to be entirely reliable. But 

 it does not seem likely that the chronopher will be introduced else- 

 where, because simpler means have been devised for splitting up the 

 current and distributing the signals. 



The whole system is under the control of the Post-Office Depart- 

 ment. They own the wires which, except in London, are the ordi- 

 nary telegraph-wires and therefore contract to keep them in order, 

 to clear them each day at the signal-times, and to deliver at these times 

 the Greenwich signal. Maintenance of lines and apparatus not the 

 property of the department is undertaken by the department for any 

 period not less than one year at specified rates. A simple form of 

 agreement has been prepared, which every renter is required to sign. 

 This agreement, as a rule, is for not less than three years, and is ter- 

 minable at three months' notice given previous to the end of the fixed 

 term, or, failing such notice, on payment of such sum as the depart- 

 ment may accept instead. But where the expense of construction is 

 considerable, the term must not be less than from five to seven years, 

 the latter period being stipulated when the proposed line is in an out- 

 lying district and would be specially provided for a single renter, and 

 when it is not probable that there would be other renters. 



The annual charges for the use of wires and apparatus are as fol- 

 lows : 



