next in
action locks it, because all the angular motion the escape wheel makes
except when in contact with the pallets is just so much lost power,
which should go toward giving motion to the balance.

There seems to be a little confusion in the use of the word "drop" in
horological phrase, as it is used to express the act of parting of the
tooth with the pallet. The idea will be seen by inspecting Fig. 108,
where we show the tooth _D_ and pallet _C_ as about parting or dropping.
When we speak of "banking up to the drop" we mean we set the banking
screws so that the teeth will just escape from each pallet. By the term
"fall" we mean the arc the tooth passes through before the next pallet
is engaged. This action is also illustrated at Fig. 108, where the tooth
_D_, after dropping from the pallet _C_, is arrested at the position
shown by the dotted outline. We designate this arc by the term "fall,"
and we measure this motion by its angular extent, as shown by the dotted
radial lines _i f_ and _i g_. As we have explained, this fall should
only extend through an arc of one and a half degrees, but by close
escapement matching this arc can be reduced to one degree, or even a
trifle less.

[Illustration: Fig. 108]

We shall next describe an instrument for holding the escape wheel and
pallets while adjusting them. As shown at Fig. 107, the fork _A'_ is
banked a little close and the jewel pin as shown would, in some
portions, rub on _C'_, making a scraping sound.

HOW TO MAKE AN ESCAPEMENT MATCHING TOOL.

[Illustration: Fig. 109]

A point has now been reached where we can use an escapement matcher to
advantage. There are several good ones on the market, but we can make
one very cheaply and also add our own improvements. In making one, the
first thing to be provided is a movement holder. Any of the three-jaw
types of such holders will answer, provided the jaws hold a movement
plate perfectly parallel with the bed of the holder. This will be better
understood by inspecting Fig. 109, which is a side view of a device of
this kind seen edgewise in elevation. In this _B_ represents the bed
plate, which supports three swing jaws, shown at _C_, Figs. 109 and 110.
The watch plate is indicated by the parallel dotted lines _A_, Fig. 109.
The seat _a_ of the swing jaws _C_ must hold the watch plate _A_ exactly
parallel with the bed plate _B_. In the cheap movement holders these
seats (_a_) are apt to be of irregular heights, and mu