aper and
called ten degrees, but when actually measured would only show eight and
a half or nine degrees.

THE PERFECTED LEVER ESCAPEMENT.

With ten degrees angular motion of the lever and one and a half degrees
lock, we should have eight and a half degrees impulse. The pith of the
problem, as regards pallet action, for the practical workman can be
embodied in the following question: What proportion of the power derived
from the twelve degrees of angular motion of the escape wheel is really
conveyed to the fork? The great leak of power as transmitted by the
lever escapement to the balance is to be found in the pallet action, and
we shall devote special attention to finding and stopping such leaks.

WHEN POWER IS LOST IN THE LEVER ESCAPEMENT.

If we use a ratchet-tooth escape wheel we must allow at least one and a
half degrees drop to free the back of the tooth; but with a club-tooth
escape wheel made as can be constructed by proper skill and care, the
drop can be cut down to three-quarters of a degree, or one-half of the
loss with the ratchet tooth. We do not wish our readers to imagine that
such a condition exists in most of the so-called fine watches, because
if we take the trouble to measure the actual drop with one of the little
instruments we have described, it will be found that the drop is seldom
less than two, or even three degrees.

If we measure the angular movement of the fork while locked, it will
seldom be found less than two or three degrees. Now, we can all
understand that the friction of the locking surface has to be counted as
well as the recoil of the draw. Locking friction is seldom looked after
as carefully as the situation demands. Our factories make the impulse
face of the pallets rounded, but leave the locking face flat. We are
aware this condition is, in a degree, necessary from the use of exposed
pallets. In many of the English lever watches with ratchet teeth, the
locking faces are made cylindrical, but with such watches the pallet
stones, as far as the writer has seen, are set "close"; that is, with
steel pallet arms extending above and below the stone.

There is another feature of the club-tooth lever escapement that next
demands our attention which we have never seen discussed. We refer to
arranging and disposing of the impulse of the escape wheel to meet the
resistance of the hairspring. Let us imagine the dotted line _A d_, Fig.
89, to represent the center of action of the fork.