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 one of the teeth of the escape wheel resting on the
pallet at the point _f_; and the escape wheel turning in the direction
of the arrow _j_. If we imagine a tooth as indicated at the dotted