19. We (as before) lay off thirty degrees on the arc
_m_ each side of the intersection of said arc with the line _A B'_, and
thus establish on the arc _m_ the points _a b_, and from _A_ as a center
draw through the points so established the radial lines _A a'_ and _A b'_.
We erect from the point _a_ a perpendicular to the line _A a_, and, as
previously explained, establish the pallet center at _B_. Inasmuch as we
are to employ circular pallets, we lay off to the left on the arc _m_,
from the point _a_, five degrees, said five degrees being half of the
angular motion of the escape wheel utilized in the present drawing, and
thus establish the point _c_, and from _A_ as a center draw through this
point the radial line _A c'_. To the right of the point _a_ we lay off
five degrees and establish the point _d_. To illustrate the underlying
principle of our circular pallets: with one leg of the dividers set at
_B_ we sweep through the points _c a d_ the arcs _c'' a'' d''_.
From _B_ as a center, we continue the line _B a_ to _f_, and with the
dividers set at five inches, sweep the short arc _e e_.
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