line _B d_ and _B c_ change places, and the tooth _D''_ locks one and a
half degrees. To delineate the locking face of the exit pallet, we erect
a perpendicular to the line _B e_ from the point _n_, as shown by the
line _n p_.

From _n_ as a center we sweep the short arc _t t_, and from its
intersection with the line _n p_ we lay off twelve degrees, and through
the point so established we draw the line _n u_, which defines the
locking face of the exit pallet. We draw the line _o o'_ parallel with
_n u_ and define the outer face of said pallet. In Fig. 21 we have not
made any attempt to show the full outline of the pallets, as they are
delineated in precisely the same manner as those previously shown.

We shall next describe the delineation of a club-tooth escapement with
pallets having equidistant locking faces; and in Fig. 22 we shall show
pallets with much wider arms, because, in this instance, we shall derive
more of the impulse from the pallets than from the teeth. We do this to
show the horological student the facility with which the club-tooth
lever escapement can be manipulated. We wish also to impress on his mind
the facts that the employment of thick pallet arms and thin pallet arms
depends on the teeth of the escape wheel for its efficiency, and that
he must have knowledge enough of the principles of action to tell at a
glance on what lines the escapement was constructed.

Suppose, for illustration, we get hold of a watch which has thin pallet
arms, or stones, if they are exposed pallets, and the escape was
designed for pallets with thick arms. There is no sort of tinkering we
can do to give such a watch a good motion, except to change either the
escape wheel or the pallets. If we know enough of the lever escapement
to set about it with skill and judgment, the matter is soon put to