67.
The ends _b b_ of the copper wire are flattened a little and recessed on
their inner faces, as shown in Fig. 70, to grasp the edges of the roller
_A_. The heat of an alcohol lamp is applied to the loop of the wire at
_g_ until the small bit of shellac placed in the hole _h_ melts. The
necessary small pieces of shellac are made by warming a bit of the gum
to near the melting point and then drawing the softened gum into a
filament the size of horse hair. A bit of this broken off and placed in
the hole _h_ supplies the cement necessary to fasten the jewel pin.
Figs. 68 and 69 will, no doubt, assist in a clear understanding of the
matter.
HOW TO MAKE AN ANGLE-MEASURING DEVICE.
We will now resume the consideration of the device for measuring the
extent of the angular motion of the fork and pallets. Now, before we
take this matter up in detail we wish to say, or rather repeat what we
have said before, which is to the effect that ten degrees of fork and
lever action is not imperative, as we can get just as sound an action
and precisely as good results with nine and a half or even nine degrees
as with ten, if other acting parts are in unison with such an arc of
angular motion.
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