below its intersection with the line _B
b_. We do not show this line in the drawing, from the fact that it comes
so near to _B b'_ that it would confuse the reader. Above the arc _a_ on
the arc _k_ at five degrees from the point _n_ we establish the point
_l_, by laying off five degrees on the arc _j_ above the intersection of
the line _B b_ with _j_.

The point _l_, Fig. 90, establishes where the outer angle of the tooth
will pass the arc _k_ to give five degrees of angular motion to the
lever. From _A_ as a center we sweep the arc _m_, passing through the
point _l_. The intersection of the arc _m_ with the line _A h_ we call
the point _r_, and by drawing the right line _r f_ we delineate the
impulse face of the tooth. On the arc _o_ and one degree below its
intersection with the line _B b_ we establish the point _t_, and by
drawing a right line from _t_ to _s_ we delineate the impulse face of
our entrance pallet.

"ACTION" DRAWINGS.

One great fault with most of our text books on horology lies in the fact
that when dealing with the detached lever escapement the drawings show
only the position of the pallets when locked, and many of the conditions
assumed are arrived at by mental processes, without making the proper
drawings to show the actual relation of the parts at the time such
conditions exist. For illustration, it is often urged that there is a
time in the action of the club-tooth lever escapement action when the
incline on the tooth and the incline on the pallet present parallel
surfaces, and consequently endure excessive friction, especially if the
oil is a little thickened.

We propose to make drawings to show the exact position and relation of
the entrance pallet and tooth at three intervals viz: (1) Locked; (2)
the position of the parts when the lever has performed one-half of its
angular motion; (3) when half of the impulse face of the tooth has
passed the pallet. The position of the entrance pallet when locked is
sufficiently well shown in Fig. 90 to give a correct idea of the
relations with the entrance pallet; and to conform to statement (2), as
above. We will now delineate the entrance pallet, not in actual contact,
however, with the pallet, because if we did so the lines we employed
would become confused. The methods we use are such that _we can
delineate with absolute correctness either a pallet or tooth at any
point in its angular motion_.

We have previously given instructions for drawing t