  The verge and foliot escapement has received relatively little attention in
horology, despite the fact that it has been used in clocks for ages. We analyse
the operation of a verge and foliot escapement in stationary swing. It is
driven by a torque $m=\pm\mu$, switching sign at fixed swing angles
$\pm\phi_0$, and $\mu$ is taken to be constant. Friction is assumed to exert a
torque proportional to the angular speed. We determine the shape of the swing
angle $\varphi(t)$, and compute the period and the swing amplitude of the
foliot analytically, as a function of the model parameters. We find that the
period of the foliot scales as $P\propto\mu^{-1}$ for weak driving, gradually
changing into $P\propto\mu^{-1/3}$ for strong driving (large $\mu$).
