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.