for delineating both forms.

With the ratchet-tooth lever escapement all of the impulse must be
derived from the pallets, but in the club-tooth escapement we can divide
the impulse planes between the pallets and the teeth to suit our fancy;
or perhaps it would be better to say carry out theories, because we have
it in our power, in this form of the lever escapement, to indulge
ourselves in many changes of the relations of the several parts. With
the ratchet tooth the principal changes we could make would be from
pallets with equidistant lockings to circular pallets. The club-tooth
escape wheel not only allows of circular pallets and equidistant
lockings, but we can divide the impulse between the pallets and the
teeth in such a way as will carry out many theoretical advantages which,
after a full knowledge of the escapement action is acquired, will
naturally suggest themselves. In the escapement shown at Fig. 20 we have
selected, as a very excellent example of this form of tooth, circular
pallets of ten degrees fork action and ten and a half degrees of
escape-wheel action.

It will be noticed that the pallets here are comparatively thin to those
in general use; this condition is accomplished by deriving the principal
part of the impulse from driving planes placed on the teeth. As relates
to the escape-wheel action of the ten and one-half degrees, which gives
impulse to the escapement, five and one-half degrees are utilized by the
driving planes on the teeth and five by the impulse face of the pallet.
Of the ten degrees of fork action, four and a half degrees relate to the
impulse face of the teeth, one and a half degrees to lock, and four
degrees to the driving plane of the pallets.

In delineating such a club-tooth escapement, we commence, as in former