2. Here
the arcs _c_, _d_, _e_ and _f_ are all fifteen degrees, although the
linear extent of the degree on the arc _c_ is twice that of the degree
on the arc _f_. When we speak of a degree in connection with a circle we
mean the one-three-hundred-and-sixtieth part of the periphery of such a
circle. In dividing the arcs _a a_ and _b b_ we first divide them into
six spaces, as shown, and each of these spaces into ten minor spaces, as
is also shown. We halve five of the degree spaces, as shown at _h_. We
should be very careful about making the degree arcs shown at Fig. 1, as
the accuracy of our drawings depends a great deal on the perfection of
the division on the scale _A_. In connection with such a fixed scale of
degrees as is shown at Fig. 1, a pair of small dividers, constantly set
to a degree space, is very convenient.
MAKING A PAIR OF DIVIDERS.
[Illustration: Fig. 3]
To make such a pair of small dividers, take a piece of hard sheet brass
about 1/20" thick, 1/4" wide, 11/2" long, and shape it as shown at Fig.
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