f course, there was a difference, and still none of the
text-books make mention of it.

For the present we will go on with delineating our exit pallet. The
preliminaries are the same as with former drawings, the instructions for
which we need not repeat. Previous to drawing the exit pallet, let us
reason on the matter. The point _r_ in Fig. 23 is located at the
intersection of pitch circle _a_ and the radial line _A c_; and this
will also be the point at which the tooth _C_ will engage the locking
face of the exit pallet.

This point likewise represents the advance angle of the engaging tooth.
Now if we measure on the arc _k_ (which represents the locking faces of
both pallets) downward one and a half degrees, we establish the lock of
the pallet _E_. To get this one and a half degrees defined on the arc
_k_, we set the dividers at 5", and from _B_ as a center sweep the
short arc _i_, and from the intersection of the arc _i_ with the line
_B e_ we lay off on said arc _i_ one and a half degrees, and through the
point so established draw the line _B f_.

Now the space on the arc _k_ between the lines _B e_ and _B f_ defines
the angular extent of the locking face. With the dividers set at 5" and
one leg resting at the point _r_, we sweep the short arc _t_, and from
the intersection of said arc with the line _A c_ we draw the line _n p_;
but in doing so we extend it (the line) so that it intersects the line
_B f_, and at said intersection is located the inner angle of the exit
pallet. This intersection we will name the point _n_.

[Illustration: Fig. 23]

From the intersection of the line _B e_ with the arc _i_ we lay off two
and a half degrees on said arc, and through the point so established we
draw the line _B g_. The intersection of this line with the arc _k_ we
name the point _z_. With one leg of our dividers set at _A_ we sweep the
arc _l_ so it passes through the point _z_. This last arc defines the
addendum of the escape-wheel teeth. From the point _r_ on the arc _a_ we
lay off three and a half degrees, and through the point so established
draw the line _A j_.

LOCATING THE OUTER ANGLE OF THE IMPULSE PLANES.

The intersection of this line with the addendum arc _l_ locates the
outer angle of the impulse planes of the teeth, and we name it the point
_x_. From the point _r_ we lay off on the arc _a_ seven degrees and
establish the point _v_, which defines the extent of the angular motion
of the escape wheel ut