Now it is a
well-known fact that the space embraced by our dividers contains exactly
sixty degrees of the arcs _a a_ and _b b_, or one-sixth of the entire
circle; consequently, we divide the arcs _a a_ and _b b_ into sixty
equal parts, to represent degrees, and at one end of these arcs we
halve five spaces so we can get at half degrees.
[Illustration: Fig. 2]
Before we take up the details of drawing an escapement we will say a few
words about "degrees," as this seems to be something difficult to
understand by most pupils in horology when learning to draw parts of
watches to scale. At Fig. 2 we show several short arcs of fifteen
degrees, all having the common center _g_. Most learners seem to have an
idea that a degree must be a specific space, like an inch or a foot. Now
the first thing in learning to draw an escapement is to fix in our minds
the fact that the extent of a degree depends entirely on the radius of
the arc we employ. To aid in this explanation we refer to Fig.
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