GREENWICH TIME AND ITS TELEGRAPHIC DISTRIBUTION. 363 
current to pass away simultaneously on each branch of the 
provincial group. There is, however, this difference : the 
distribution in London takes place at every hour, the wires 
being used for time-signal purposes only ; but for the country, 
as it would at present be too expensive to employ special wires, 
those of the ordinary telegraphic service are used, general dis- 
tribution of time on these wires being made once each day 
only, at 10 h. a.m. Every care is taken that this distribution 
shall be effective and certain. The chronopher includes 
arrangements by which (by means of a clock) the various pro- 
vincial wires are, immediately before 10 h., automatically dis- 
connected, each from its particular speaking instrument, and 
placed in communication with the chronopher commutator, in 
readiness for the Greenwich current. When it has passed and 
distributed time currents throughout the provincial lines, the 
ordinary connections of the lines, are again automatically re- 
stored. And amongst minor arrangements there is one for 
preventing, almost entirely, interruption from accidental gal- 
vanic current arising, in any way, in the Greenwich wire. 
These 10 h. currents, being distributed along the principal 
lines of railway, give time daily through a large extent of 
country ; they are used, to a considerable extent, for the direct 
correction of railway clocks, and indirectly rule them all, these 
clocks acting again each as a standard for the clocks of the 
neighbouring districts. 
In some instances currents distributed from the .Central 
Telegraph Office have been used for giving time to the public 
by public signal. In the year 1863 the River Tyne Commis- 
sioners promoted the establishment of two such signals, which 
have proved to be of great value. A 12-pounder gun at New- 
castle and a 24-pounder gun at North Shields have, since the 
year mentioned, been fired daily at 1 h. p.m. Greenwich time. At 
London the chronopher, by automatic action, places the New- 
castle wire for a short time in proper state to be acted on by 
the Greenwich 1 h. current ; at Newcastle proper changes of the 
speaking circuits are there also automatically made. As soon 
as at lh. the seconds hand of the Greenwich normal clock 
marks 60, the relays at Greenwich, London, and Newcastle 
will each successively act, and galvanic currents will pass to the 
guns and fire them before the sound of the clock beat at Green- 
wich has well died away. The fuse used for the guns is Abel’s 
chemical fuse, which explodes on passage through it of a gal- 
vanic current. Two fuses are inserted daily at each gun, to avoid 
failure should one of them by accident miss fire.* 
* In taking time by the sound of a gun it is of course necessary to allow 
seconds for each mile that the gun is distant from the observer. 
