. Some of the other specimens of this
escapement have larger arcs--some as high as twelve degrees.

PALLET-AND-FORK ACTION.

[Illustration: Fig. 5]

We illustrate at Fig. 5 what we mean by ten degrees of pallet-and-fork
action. If we draw a line through the center of the pallet staff, and
also through the center of the fork slot, as shown at _a b_, Fig. 5, and
allow the fork to vibrate five degrees each side of said lines _a b_, to
the lines _a c_ and _a c'_, the fork has what we term ten-degree pallet
action. If the fork and pallets vibrate six degrees on each side of the
line _a b_--that is, to the lines _a d_ and _a d'_--we have twelve
degrees pallet action. If we cut the arc down so the oscillation is only
four and one-quarter degrees on each side of _a b_, as indicated by the
lines _a s_ and _a s'_, we have a pallet-and-fork action of eight and
one-half degrees; which, by the way, is a very desirable arc for a
carefully-constructed escapement.

The controlling idea which would seem to rule in constructing a detached
lever escapement, would be to make it so the balance is free of the
fork; that is, detached, during as much of the arc of the vibration of
the balance as possible, and yet have the action thoroughly sound and
secure. Where a ratchet-tooth escapement is thoroughly well-made of
eight and one-half degrees of pallet-and-fork action, ten and one-half
degrees of escape-wheel action can be utilized, as will be explained
later on.

We will now resume the drawing of our escape wheel, as illustrated at
Fig. 4. In the drawing at Fig. 6 we show the circle _n n_, which
represents the periphery of our escape wheel; and in the drawing we are
supposed to be drawing it ten inches in diameter.

We produce the vertical line _m_ passing through the center _p_ of the
circle _n_. From the intersection of the circle _n_ with the line _m_
at _i_ we lay off thirty degrees on each side, and establish the points
_e f_; and from the center _p_, through these points, draw the radial
lines _p e'_ and _p f'_. The points _f e_, Fig. 6, are, of course, just
sixty degrees apart and represent the extent of two and one-half teeth
of the escape wheel. There are two systems on which pallets for lever
escapements are made, viz., equidistant lockings and circular pallets.
The advantages claimed for each system will be discussed subsequently.
For the first and present illustration we will assume we are to employ
circular pallets and o