ency on the part of the pallet to turn on its axis _B_.
Theoretically, the pallet with the locking face cut to coincide with the
line _A b_ would resist movement on the center _B_ in either direction
indicated by the double-headed arrow _y_.

A pallet at _C_ with a circular locking face made to conform to the arc
_g_, would permit movement in the direction of the double-headed arrow
_y_ with only mechanical effort enough to overcome friction. But it is
evident on inspection that a locking face on the line _A b_ would cause
a retrograde motion of the escape wheel, and consequent resistance, if
said pallet was moved in either direction indicated by the double-headed
arrow _y_. Precisely the same conditions obtain at the point _u_, which
holds the same relations to the exit pallet as the point _o_ does to the
entrance pallet _C_.

ANGULAR MOTION OF ESCAPE WHEEL DETERMINED.

The arc (three and a half degrees) of the circle _a_ embraced between
the radial lines _A b_ and _A e_ determines the angular motion of the
escape wheel utilized by the escape-wheel tooth. To establish and define
the extent of angular motion of the escape wheel utilized by the pallet,
we lay off seven degrees on the arc _a_ from the point _o_ and establish
the point _n_, and through the point _n_, from _B_ as a center, we sweep
the short arc _n'_. Now somewhere on this arc _n'_ will be located the
inner angle of the entrance pallet. With a carefully-made drawing,
having the escape wheel 10" in diameter, it will be seen that the arc
_a_ separates considerably from the line, _B f'_ where it crosses the
arc _n'_.

It will be remembered that when drawing the ratchet-tooth lever
escapement a measurement of eight and a half degrees was made on the arc
_n'_ down from its intersection with the pitch circle, and thus the
inner angle of the pallet was located. In the present instance the
addendum line _w_ becomes the controlling arc, and it will be further
noticed on the large drawing that the line _B h_ at its intersection
with the arc _n'_ approaches nearer to the arc _w_ than does the line
_B f'_ to the pitch circle _a_; consequently, the inner angle of the pallet
should not in this instance be carried down on the arc _n'_ so far to
correct the error as in the ratchet tooth.

Reason tells us that if we measure ten degrees down on the arc _n'_ from
its intersection with the addendum circle _w_ we must define the
position of the inner angle of the entranc