186 | Ff A. P. Barnard on the Pendulum. 
impose a certain duty on the pendulum, which is, to unlock the 
—whereby error is introduced into the time shown upon the dial, 
Of all these escapements, remontoir escapements and pallet 
those occasioned by the varying temperature and density of the 
air, e usual extent of the arc of vibration is 2° on each side 
merely to unlock the train of the remontoir. If now, at a defi 
nite point of the swing, a light weight could be deposited upon 
b 
accelerating or retarding but such as may be accurately estimated 
in their amount, and in their effects upon the time of vibration. 
perature, a special compensation may be made. 
he Problem which is here proposed, seems to present we 
ifficult to be fulfilled. The impulse is to come at ti 
proper moment, but the pendulum is to do no work in 0 ich 
induce it. Yet it can be nothing but the poses ae 
