the single roller. We will
find the length of horn; to do so we must closely follow directions
given for Fig. 25. In locating the end of the horn, we must find the
location of the center of the crescent and ruby pin _after_ the edge of
the crescent has passed the dart. From the point of intersection of
A' _b_ with the safety roller we transfer the radius of the crescent on
the periphery of the safety roller towards the side against the bank,
then draw a line from A' through the point so found. At point of
intersection of this line with the real impulse circle _r i r i_ we draw
an arc radiating from the pallet center; the end of the horn will be
located on this arc. In our drawing the arc spoken of coincides with the
dart radius _g g_. As before pointed out, we gave particulars when
treating on Fig. 25, therefore considered it unnecessary to further
complicate the draft by the addition of all the constructional lines. We
specified that the freedom between ruby pin and end of horn was to be
1 1/2deg.; these lines, (which we do not show) are drawn from the pallet
center. Having located the end of the horn on the side standing against
the bank, we place the dividers on it and on the point of intersection
of _k_ A with _g g_--which in this case is on the point of the
dart,--and transfer this measurement along _g g_ which will locate the
end of the horn on the opposite side.

We have the acting edges of the fork on _cc_ and have also found the
position of the ends of the horns; their curvature is drawn in the
following manner: We place our compasses on A and _r i_, spanning
therefore the real impulse radius; the compass is now set on the acting
edge of the fork and an arc swept with it which is then to be
intersected by another arc swept from the end of the horn, on the same
side of the fork. At the point of intersection of the arcs the compass
is planted and the curvature of the horn drawn in, the same operation is
to be repeated with the other horn. We will now draw in the sides of the
horn of such a form that should the watch rebank, the side of the ruby
pin will squarely strike the fork. If the back of the ruby pin strikes
the fork there will be a greater tendency of breaking it and injuring
the pivots on account of acting like a wedge. The fork and pallets are
now drawn in as lightly as possible and of such form as to admit of
their being readily poised. The banks are to be drawn at equal distances
from the line of cente