ations of
oscillation quite without interference, and it is only in contact with
the train during the very brief moment of impulse which is needful to
keep the regulating organ in motion. This category constitutes what is
known as the _detached escapement_ class.

Of the _recoil escapement_ the principal types are: the _verge
escapement_ or _crown-wheel escapement_ for both watches and clocks, and
the _recoil anchor escapement_ for clocks. The _cylinder_ and _duplex
escapements_ for watches and the _Graham anchor escapement_ for clocks
are styles of the _dead-beat escapement_ most often employed. Among the
_detached escapements_ we have the _lever_ and _detent_ or _chronometer
escapements_ for watches; for clocks there is no fixed type of detached
lever and it finds no application to-day.

THE VERGE ESCAPEMENT.

The _verge escapement_, called also the _crown-wheel escapement_, is by
far the simplest and presents the least difficulty in construction. We
regret that the world does not know either the name of its originator
nor the date at which the invention made its first appearance, but it
seems to have followed very closely upon the birth of mechanical
horology.

Up to 1750 it was employed to the exclusion of almost all the others. In
1850 a very large part of the ordinary commercial watches were still
fitted with the verge escapement, and it is still used under the form of
_recoil anchor_ in clocks, eighty years after the invention of the
cylinder escapement, or in 1802. Ferdinand Berthoud, in his "History of
the Measurement of Time," says of the balance-wheel escapement: "Since
the epoch of its invention an infinite variety of escapements have been
constructed, but the one which is employed in ordinary watches for
every-day use is still the best." In referring to our illustrations, we
beg first to call attention to the plates marked Figs. 145 and 146.
This plate gives us two views of a verge escapement; that is, a balance
wheel and a verge formed by its two opposite pallets. The views are
intentionally presented in this manner to show that the verge _V_ may be
disposed either horizontally, as in Fig. 146, or vertically, as in Fig.
145.

[Illustration: Figs. 145 and 146]

[Illustration: Fig. 147]

Let us imagine that our drawing is in motion, then will the tooth _d_,
of the crown wheel _R_, be pushing against the pallet _P_, and just upon
the point of slipping by or escaping, while the opposite tooth _e_ is