f and for
additional security has a pipe or short socket _e_ which embraces the
balance staff at _g_. The pipe _e_ is usually flattened on opposite
sides to admit of employing a special wrench for turning the discharging
roller in adjusting the jewel for opening the escapement at the proper
instant to permit the escape wheel to act on the impulse jewel _a_. The
parts which go to make up the detent _D_ consist of the "detent foot"
_F_, the detent spring _h_, the detent blade _i_, the jewel pipe _j_,
the locking jewel (or stone) _s_, the "horn" of the detent _k_, the
"gold spring" (also called the auxiliary and lifting spring) _m_. This
lifting or gold spring _m_ should be made as light and thin as possible
and stand careful handling.

We cannot impress on our readers too much the importance of making a
chronometer detent light. Very few detents, even from the hands of our
best makers, are as light as they might be. We should in such
construction have very little care for clumsy workmen who may have to
repair such mechanism. This feature should not enter into consideration.

We should only be influenced by the feeling that we are working for best
results, and it is acting under this influence that we devote so much
time to establishing a correct idea of the underlying principles
involved in a marine chronometer, instead of proceeding directly to the
drawing of such an escapement and give empirical rules for the length of
this or the diameter of that. As, for instance, in finishing the detent
spring _h_, suppose we read in text books the spring should be reduced
in thickness, so that a weight of one pennyweight suspended from the
pipe _j_ will deflect the detent 1/4". This is a rule well enough for
people employed in a chronometer factory, but for the horological
student such fixed rules (even if remembered) would be of small use.
What the student requires is sound knowledge of the "whys," in order
that he may be able to thoroughly master this escapement.

FUNCTIONS OF THE DETENT.

We can see, after a brief analysis of the principles involved, that the
functions required of the detent _D_ are to lock the escape wheel _A_
and hold it while the balance performs its excursion, and that the
detent or recovering spring _h_ must have sufficient strength and power
to perform two functions: (1) Return the locking stone _s_ back to the
proper position to arrest and hold the escape wheel; (2) the spring _h_
must also be able t