With this new
system it became possible to increase the weight of the bob and at the
same time lessen the effective motor power. The travel of the pendulum,
or arc of oscillation, being reduced in a marked degree, an accuracy of
rate was obtained far superior to that of the crown-wheel escapement.
However, this new application of the recoil escapement was not adopted
in France until 1695.
[Illustration: Fig. 166]
[Illustration: Fig. 167]
The travel of the pendulum, though greatly reduced, still surpassed in
breadth the arc in which it is isochronous, and repeated efforts were
made to give such shape to the levers as would compel its oscillation
within the arc of equal time; a motion which is, as was recognized even
at that epoch, the prime requisite to a precise rating. Thus, in 1720,
Julien Leroy occupied himself working out the proper shapes for the
inclines to produce this desired isochronism. Searching along the same
path, Ferd. Berthoud constructed an escapement represented by the Fig.
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