F. A. P, Barnard on the Pendulum. 189 
change of position within the second. A stop prevents the spring 
(from following the hook as it rises. 
. When the impulse weight A’ is deposited on the hooks, it is 
the magnet Af which acts; and the effects of this, through the 
bent lever pivoted at Z, is to release the governor, which, by its 
preponderant weight will cause the remontoir to tilt again. 
_ Whenever either magnet acts, the magnet of the time-register 
oom acts, and advances the second-hand one division 
on the dia 
The remaining parts of the mechanism it is hardly necéssary_ 
to describe. Adjusting screws are provided to secure the exact 
position of the pendulum arms, and to cause the impul be 
precisely equal in duration on opposite sides. In adjusting for 
this latter purpose, the graduated arc on the right, and the index 
attached to the remontoir lever, are employed. The manner of 
making the adjustment is obvious. ; 
endulum impelled in this manner is subject to the action 
of no forces which cannot be definitely appreciated. The im- 
pelling power is constant and known. The mean resistance of 
the air may be com uted, and even its fluctuations may, 1 
necessary, be taken into account. The irregularities, therefore, 
Which cannot be ascribed to these causes, must be due to im- 
perfect compensation. 
ere is a possibility that a steel pendulum rod may, to some 
Ploy ed in this contrivance. In order to guard against this danger, 
fit be one, the rod of the pendulum of the clock, here exhibited, 
8 made of brass; and the compensation, which is mercurial, is 
adjusted accordingly. ; 
The effect of the impelling and resisting forces acting upon a 
Pendulum is to alter its rate of motion; but this circumstance 1s 
gravity, f however, any variation occurs, either in the impulse 
| t * . . * 
ip lerates the rate of going of the pendulum, it applies invari- 
t 
