254 Chronicles of Science. | April, 
of regulating clocks is exclusively used. It is generally known 
that, according to this method, the electric fluid is employed merely 
as a regulating agent, and not in any case as a motive power, the 
time-piece under control being an ordinary clock, connected by a 
regular succession of electric pulsations with the normal mean-time 
clock of the Observatory. ‘The application of the invention in 
Glasgow has been perfectly successful. It has been employed under 
various forms; but what Professor Grant considered to be the most 
suitable to the requirements of a large city was the small clock with 
a seconds’ pendulum and a dial of about three feet in diameter, 
showing the time to hours, minutes, and seconds. Ciocks of this 
construction have been set up in the public thoroughfares of 
Glasgow, and have been found to be exceedingly useful. Attached 
to each of them is a galvanometer, which, by its deflections, gives an 
indication of the electric currents transmitted m successive seconds 
from the normal mean-time clock of the Observatory, and a break 
in the transmission of the currents, once in every minute, namely, 
at the sixtieth second, of the Observatory clock, supplies the public 
with an unerring criterion for testing the accuracy of the controlled 
clock. There were now eleven clocks of various forms in Glasgow 
under the electric control of the mean-time clock of the Observatory. 
In a short time the number would be increased to some seventeen 
or eighteen, and the system was gradually extending over all 
Glasgow. The going of these clocks was truly marvellous. From 
week to week and from month to month they continued to mdicate 
the time with the utmost precision, requirmg merely a little 
attention now and then to the battery power. It was one of the 
advantages of Jones's method of control that, even in the case 
where the operations were on an extensive scale, only a small 
amount of battery power was necessary. There was one other 
remark which he would make, and it had reference to turret-clocks. 
Hitherto it had been usual, in the operations for placing one of such 
clocks under control, to remove the two seconds’ pendulum, and to 
substitute for it a seconds’ pendulum, which was made to beat in 
exact unison with the pendulum of the Observatory clock. Objec- 
tions to this practice have been expressed by many persons who 
consider that a heavy pendulum vibrating once in two seconds is 
much better adapted than a light seconds’ pendulum for maintain- 
ing the steady going of a clock fitted up in a lofty tower, the dials 
and hands of which are necessarily exposed very much to the action 
of high winds. After a good deal of experiment, Professor Grant 
found that the two seconds’ pendulum might be retained and kept 
under complete control by attaching a large wire coil to the bob, 
and using a more powerful system of magnets in combination 
with it. 
Messrs. Warren De la Rue, Stewart, and Loewy have examined 
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