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TRANSACTIONS OF THE SECTIONS. 13 
cited by a single cell less than it would be without a condenser, will increase the effect 
of the same coil, when it is connected with a battery of ten or twelve cells, 
On controlling the Movements of Ordinary Clocks by Galvanic Currents. 
By Joun Hartnup, F.R.A.S. 
Since the application of electricity to the purposes of the telegraph, various 
methods have been employed for working clocks at distant stations by a normal 
clock at an observatory, or by causing one clock in a large establishment to work 
_ several sympathetic clocks in different parts of the building. The advantage of being 
able to make several clocks show the same time as a normal clock regulated by 
astronomical observations, or by the transmission of time signals from an observa- 
tory, must be admitted to be great; but those who have had much practical experi- 
ence in the matter are aware of the serious drawback which, in spite of every pre- 
caution, will occasionally arise from failure in thefgalvanic current, and which neces- 
sarily causes all the sympathetic clocks to stop. We think, therefore, that the 
members of the British Association for the Advancement of Science will be gratified 
to hear of an invention which sacrifices nothing in point of accuracy, and which is, 
nevertheless, perfectly exempt from the objection to which we have alluded. 
For the discovery of this simple and very beautiful method, we are indebted to 
Mr. R. L. Jones, of Chester; and the first application of it to a large public clock 
was to that of the Liverpool Town Hall. This clock being appealed to by the mer- 
chants on change as the standard of time, had subjected them to great incon- 
venience by its irregular performance, and at my recommendation the plan of Mr. 
Jones has been adopted with perfect success. The clock in its present state, with 
the improvements which have been made, differs in no respect from an ordinary old 
turret clock, except that the pendulum-bob is a hollow electro-magnetic coil, which 
_ passes around permanent magnets at each oscillation. At each transmission of a 
current from our normal clock at the Observatory, the coil itself becomes a magnet, 
and the attraction or repulsion between it and the permanent magnet prevents the 
pendulum from oscillating except in strict conformity with the pendulum at the 
Observatory. The wire which connects the Town Hall clock with the clock at the 
Observatory is about one mile in length, and the controlling power is so great, that a 
single cell of a Smee’s battery charged with very weak acid is sufficient to control 
the movements of the Town Hall clock, even when the pendulum is lengthened or 
shortened so as to make it lose or gain several minutes a day when not under the 
control of the clock at the Observatory. In practice, however, the pendulum is 
regulated to correct time as near as possible, so that in the event of the current 
failing, the clock will not only continue to go, but it is liable to the errors only of an 
ordinary clock; and as an error so small even as a fraction of a second is sufficient 
to show that the current is not controlling, the fault may be detected and the remedy 
applied before the public are subjected to any inconvenience. 
By this method therefore it is quite practicable to make all the public clocks in a 
town, Or any number of clocks in a large building, strike, or keep the same time to a 
fraction of a second, without the risk of inconvenience by failure of the electric 
current, since all the clocks would go as ordinary clocks should the current fail. 
This method of controlling the pendulum of a large public clock has been in opera- 
tion at Liverpool for several months past, and the public have an opportunity each 
hour of the day of witnessing the efficiency of the method. In the office window of 
the Magnetic Telegraph Company, which is within a few yards of the Liverpool 
Town Hall, there is a sympathetic seconds clock, the face of which is exhibited to 
the public. his clock is worked by our normal clock at the Observatory ; and as 
the seconds’ hand, at the end of each hour, falls upon the sixtieth second, the first 
blow of the hammer of the Town Hall clock breaks upon the ear, much to the 
admiration and astonishment of a large number of persons who congregate daily to 
witness this novel performance. 
The normal clock at the Observatory is an ordinary astronomical clock, the con- 
tact-springs of which are so slight as not to interfere sensibly with its performance. 
It will be seen, therefore, that by placing a good astronomical clock in any build- 
ing, a turret or any other clocks may be connected and their movements controlled 
by it, and a degree of accuracy secured which has hitherto not been attained. 
