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marks 60. So that only at the instant of each hour are both 
breaks together united, and only then can a galvanic current 
pass. Each hourly current acts upon two electro-magnets. 
One is used at 1 h. p.m. only, to discharge the Greenwich time 
ball. The other has a far more extended use : by relay * ac- 
tion it completes two other galvanic circuits, each giving 
hourly signals on a separate line of wire. One of these lines 
is in communication with the Central Postal Telegraph Office 
in Telegraph Street, London ; the other passes to the London 
Bridge Station of the South-Eastern Eailway. Hourly time- 
signals pass from the Eoyal Observatory along these lines day 
and night, and with the efficient performance of this duty the 
special responsibility of the Observatory terminates, the further 
distribution of the signals thus transmitted being under the 
control of other parties. [In speaking of “currents” and 
“ signals,” proper distinction cannot always be preserved, 
although, strictly speakings by “current” we understand the 
unseen something which conventionally is supposed to pass 
along a wire ; by “ signal ” the effect which the unseen current 
produces upon a telegraph needle or other indicator.] 
The use made of the hourly signals in each of these lines 
must be considered separately. Taking that first mentioned, 
we proceed now to explain that in the Central Telegraph Office 
there is fixed an admirable and elaborate apparatus, designed 
by and constructed under the superintendence of Mr. C. F. 
Varley, engineer to the then existing Electric and International 
Telegraph Company, for the purpose, as he himself explains, 
“ of sending exact Greenwich time simultaneously and automa- 
tically to numerous local and provincial stations.” The whole 
collection of apparatus is known as the “ Chronopher.” It 
acts as a gigantic switch and relay, and by its means the 
one Greenwich current is transmitted on many different lines. 
These lines are, for convenience, disposed in two groups — one 
consisting of wires passing to points in London, the other of 
wires extending to distant parts of the kingdom, including 
such places as Manchester, Birmingham, &c. For the service 
of these groups of wires there are two relays — one the “ local ” 
relay for the London group, the other the “ provincial ” relay 
for the country group. On these relays only does the Green- 
wich time current act. In the local relay it causes a current 
to pass away simultaneously on each branch of the London 
group of wires ; similarly in the provincial relay it causes a 
• In its simple form the relay is an instrument which, on receipt of a 
galvanic current — which may be from a distance — completes the circuit of 
a battery of its own, either for transmission of a signal to another station, or 
for the performance of some mechanical work. 
