The verge _V_ was set up
horizontally and the pendulum _B_, suspended freely from a flexible
cord, received the impulses through the intermediation of the forked arm
_F_, which formed a part of the verge. At first this forked arm was not
thought of, for the pendulum itself formed a part of the verge. A
far-reaching step had been taken, but it soon became apparent that
perfection was still a long way off. The crown-wheel escapement forcibly
incited the pendulum to wider oscillations; these oscillations not being
as Galileo had believed, of unvaried durations, but they varied sensibly
with the intensity of the motive power.
THE ATTAINMENT OF ISOCHRONISM BY HUYGENS.
Huygens rendered his pendulum _isochronous_; that is, compelled it to
make its oscillations of equal duration, whatever might be the arc
described, by suspending the pendulum between two metallic curves _c
c'_, each one formed by an arc of a cycloid and against which the
suspending cord must lie upon each forward or backward oscillation.
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