ere on
the line E B there would be no draw, and if placed to the opposite side
of E B the tooth would repel the pallet, forming what is known as the
repellant escapement.

[Illustration: Fig. 28.]

Having shown how to delineate the locking face of the engaging pallet
when locked, we will now consider how to draft both it and the
disengaging pallet in correct positions when unlocked; to do so we
direct our attention until further notice to Fig. 28. The locking faces
Q M of the engaging and S N of the disengaging pallets are shown in
dotted lines _when locked_. We must now consider the relation which the
locking faces will bear to E B in the engaging, and to F B in the
disengaging pallets when unlocked. This is a question of some
importance; it is easy enough to represent the 12deg. from the 30deg.
angles when locked; we must be certain that they would occupy exactly
that position and yet show them unlocked; we shall take pains to do so.
In due time we shall show that there is no appreciable loss of lift on
the engaging pallet in the escapement illustrated; the angle T A V
therefore shows the total lift; we have not shown the corresponding
angles on the disengaging side because the angles are somewhat
different, but the total lift is still the same. G H represents the
primitive circle of the escape wheel, and X Z that of the real, while
M N represents the circular course which the locking corners of the
pallets take in an equidistant escapement. At a convenient position we
will construct the circle C C' D from the pallet center A. Notice the
points _e_ and _c_, where V A and T A intersect this circle; the space
between _e_ and _c_ represents the extent of the motion of the pallets
at this particular distance from the center A; this being so, then let
us apply it to the engaging pallet. At the point of intersection _o_ of
the dotted line Q M (which is an extended line on which the face of the
pallet lies when locked), with the circle C C' D, we will plant our
dividers and transfer _e c_ to _o n_. By setting our dividers on _o_ M
and transferring to _n_ M', we will obtain the location of Q' M', the
locking face when unlocked. Let us now turn our attention to the
disengaging pallet. The dotted line S N represents the location of the
locking face of the disengaging pallet when locked at an angle of 12deg.
from F B. At the intersection of S N with the circle C C' D we obtain
the point _j_. The motion of the two pallets being