n accomplished, the locking takes place upon the pin _C_
of the other wheel upon the pallet _P'_. Another system of two escape
wheels is shown in Fig. 160, but in this case the two wheels _R R_ are
driven in a like direction by the last wheel _A_ of the train. The
operation of the escapement is the same as in Fig. 159.

[Illustration: Fig. 164]

[Illustration: Fig. 165]

In Fig. 161 we have a departure from the road ordinarily pursued. Here
we see an escapement combining two levers, invented by the Chevalier de
Bethune and applied by M. Thiout, master-horologist, at Paris in 1727.
_P P'_ are the two levers or pallets separately pivoted. Upon the axis
_V_, of the lever _P_, is fixed a fork which communicates the motion to
the pendulum. The two levers are intimately connected by the two arms _B
B'_, of which the former carries an adjusting screw, a well-conceived
addition for regulating the opening between the pallets. The
counter-weight _C_ compels constant contact between the arms _B B'_. The
function is always the same, the recoil and the impulsion operate upon
the two pallets simultaneously. This escapement enjoyed a certain degree
of success, having been employed by a number of horologists who modified
it in various ways.

VARIOUS MODIFICATIONS

Some of these modifications we shall show. For the first example, then,
let Fig. 162 illustrate. In this arrangement the fork is carried upon
the axis of the pallet _P'_, which effectually does away with the
counter-weight _C_, as shown. Somewhat more complicated, but of the same
intrinsic nature, is the arrangement displayed in Fig. 163. We should
not imagine that it enjoyed a very extensive application. Here the two
levers are completely independent of each other; they act upon the piece
_B B_ upon the axis _V_ of the fork. The counter-weights _C C'_ maintain
the arms carrying the rollers _D D'_ in contact with the piece _B B'_
which thus receives the impulse from the wheel _R_. Two adjusting screws
serve to place the escapement upon the center. By degrees these
fantastic constructions were abandoned to make way for the anchor recoil
escapement, which was invented, as we have said, in 1675, by G. Clement,
a horologist, of London. In Fig. 164 we have the disposition of the
parts as first arranged by this artist. Here the pallets are replaced by
the inclines _A_ and _B_ of the anchor, which is pivoted at _V_ upon an
axis to which is fixed also the fork. The tooth _a_ e