educate the eye to discriminate not only as to correct actions, but also
to detect those which are imperfect, and we believe most watchmakers
will admit that in many instances it takes much longer to locate a fault
than to remedy it after it has been found.

[Illustration: Fig. 55]

Let us now proceed to delineate a fork and roller. It is not imperative
that we should draw the parts to any scale, but it is a rule among
English makers to let the distance between the center of the pallet
staff and the center of the balance staff equal in length the chord of
ninety-six degrees of the pitch circle of the escape wheel, which, in
case we employ a pitch circle of 5" radius, would make the distance
between _A_ and _B_, Fig. 55, approximately 7½", which is a very fair
scale for study drawings.


HOW TO DELINEATE A FORK AND ROLLER.

To arrive at the proper proportions of the several parts, we divide the
space _A B_ into four equal parts, as previously directed, and draw the
circle _a_ and short arc _b_. With our dividers set at 5", from _B_ as a
center we sweep the short arc _c_. From our arc of sixty degrees, with a
5" radius, we take five degrees, and from the intersection of the right
line _A B_ with the arc _c_ we lay off on each side five degrees and
establish the points _d e_; and from _B_ as a center, through these
points draw the lines _B d'_ and _B e'_. Now the arc embraced between
these lines represents the angular extent of our fork action.

From _A_ as a center and with our dividers set at 5", we sweep the arc