eg., the point or locking edge of the tooth would rapidly
become worn in case of a brass wheel. Also in an English lever more drop
would be required.

_The Lock._--What we have said in regard to drop also applies to the
lock, which should be as small as possible, consistent with perfect
safety. The greater the drop the deeper must be the lock; 1 1/2deg. is the
angle generally allowed for the lock, but it is obvious that in a large
escapement it can be less.

[Illustration: Fig. 6.]

_The Run._--The run or, as it is sometimes called, "the slide," should
also be as light as possible; from 1/4deg. to 1/2deg. is sufficient. It
follows then, the bankings should be as close together as possible,
consistent with requisite freedom for escaping. Anything more than this
increases the angular connection of the balance with the escapement,
which directly violates the theory under which it is constructed; also,
a greater amount of work will be imposed upon the balance to meet the
increased unlocking resistance, resulting in a poor motion and accurate
time will be out of the question. It will be seen that those workmen who
make a practice of opening the banks, "to give the escapement more
freedom" simply jump from the frying pan into the fire. The bankings
should be as far removed from the pallet center as possible, as the
further away they are pitched the less run we require, according to
angular measurement. Figure 6 illustrates this fact; the tooth S has
just dropped on the engaging pallet, but the fork has not yet reached
the bankings. At _a_ we have 1deg. of run, while if placed at _b_ we
would only have 1/2deg. of run, but still the same freedom for escaping,
and less unlocking resistance.

The bankings should be placed towards the acting end of the fork as
illustrated, as in case the watch "rebanks" there would be more strain
on the lever pivots if they were placed at the other end of the fork.

[Illustration: Fig. 7.]

_The Lift._--The lift is composed of the actual lift on the teeth and
pallets and the lock and run. We will suppose that from drop to drop we
allow 10deg.; if the lock is 1 1/2deg. then the actual lift by means of the
inclined planes on teeth and pallets will be 8 1/2deg. We have seen that a
small lifting angle is advisable, so that the vibrations of the balance
will be as free as possible. There are other reasons as well. Fig. 7
shows two inclined planes; we desire to lift the weight 2 a distance
equal