e, shown at _C_, Figs. 24 and 25, is 1/8"
thick and shaped as shown. This plate (_C_) is supported on two pillars
1/2" in diameter and 11/4" high. Fig. 25 is a side view of Fig. 24 seen
in the direction of the arrow _p_. The cock _D_ is also of 1/8" spring
brass shaped as shown, and attached by the screw _f_ and steady pins _s s_
to the top plate _C_. The bridge _F G_ carries the top pivots of
escape wheel and pallet staff, and is shaped as shown at the full
outline. This bridge is supported on two pillars 1/2" high and 1/2" in
diameter, one of which is shown at _E_, Fig. 25, and both at the dotted
circles _E E'_, Fig. 24.

To lay out the lower plate we draw the line _a a_ so it passes through
the center of _A_ at _m_. At 1.3" from one edge of _A_ we establish on
the line _a_ the point _d_, which locates the center of the escape
wheel. On the same line _a_ at 1.15" from _d_ we establish the point
_b_, which represents the center of the pallet staff. At the distance of
1.16" from _b_ we establish the point _c_, which represents the center
of the balance staff. To locate the pillars _H_, which support the top
plate _C_, we set the dividers at 2.58", and from the center _m_ sweep
the arc _n_.

From the intersection of this arc with the line _a_ (at _r_) we lay off
on said arc _n_ 2.1" and establish the points _g g'_, which locate the
center of the pillars _H H_. With the dividers set so one leg rests at
the center _m_ and the other leg at the point _d_, we sweep the arc _t_.
With the dividers set at 1.33" we establish on the arc _t_, from the
point _d_, the points _e e'_, which locate the position of the pillars
_E E'_. The outside diameter of the balance _B_ is 3-5/8" with the rim
3/16" wide and 5/16" deep, with screws in the rim in imitation of the
ordinary compensation balance.

Speaking of a balance of this kind suggests to the writer the trouble he
experienced in procuring material for a model of this kind--for the
balance, a pattern had to be made, then a casting made, then a machinist
turned the casting up, as it was too large for an American lathe. A
hairspring had to be specially made, inasmuch as a mainspring was too
short, the coils too open and, more particularly, did not look well.
Pallet jewels had to be made, and lapidists have usually poor ideas of
close measurements. Present-day conditions, however, will, no doubt,
enable the workman to follow our instructions much more readily.

MAKING THE BRIDGES.