le
construction. Back of the slot of the fork, which is three-fifths of the
diameter of the jewel pin in depth, is made a square hole, as shown at
_u_, and the back end of the guard point _C_ is fitted to this hole so
that it is rigid in position. This manner of fastening the guard point
is equally efficient as that of attaching it with a screw, and much
lighter--a matter of the highest importance in escapement construction,
as we have already urged. About the best material for such guard points
is either aluminum or phosphor bronze, as such material is lighter than
gold and very rigid and strong. At Fig. 83 we show a side view of the
essential parts depicted in Fig. 82, as if seen in the direction of the
arrow _v_, but we have added the piece which holds the jewel pin _D_. A
careful study of the cut shown at Fig. 82 will soon give the horological
student an excellent idea of the double-roller action.

We will now take up and consider at length why Saunier draws his
entrance pallet with fifteen degrees draw and his exit pallet with only
twelve degrees draw. To make ourselves more conversant with Saunier's
method of delineating the lever escapement, we reproduce the essential
features of his drawing, Fig. 1, plate VIII, of his "Modern Horology,"
in which he makes the draw of the locking face of the entrance pallet
fifteen degrees and his exit pallet twelve degrees. In the cut shown at
Fig. 84 we use the same letters of reference as he employs. We do not
quote his description or directions for delineation because he refers to
so much matter which he has previously given in the book just referred
to. Besides we cannot entirely endorse his methods of delineations for
many reasons, one of which appears in the drawing at Fig. 84.

[Illustration: Fig. 84]

MORE ABOUT TANGENTIAL LOCKINGS.

Most writers endorse the idea of tangential lockings, and Saunier speaks
of the escapement as shown at Fig. 84 as having such tangential
lockings, which is not the case. He defines the position of the pallet
staff from the circle _t_, which represents the extreme length of the
teeth; drawing the radial lines _A D_ and _A E_ to embrace an arc of
sixty degrees, and establishing the center of his pallet staff _C_ at
the intersection of the lines _D C_ and _E C_, which are drawn at right
angles to the radial lines _A D_ and _A E_, and tangential to the circle
_t_.

Here is an error; the lines defining the center of the pallet staff
should