ly worth the extra trouble. Rollers for
very fine watches should be poised on the staff before the balance is
placed upon it.

[Illustration: Fig. 80]

We shall next give detailed instructions for drawing such a double
roller as will be adapted for the large model previously described,
which, as the reader will remember, was for ten degrees of roller
action. We will also point out the necessary changes required to make it
adapted for eight degrees of fork action. We would beg to urge again the
advantages to be derived from constructing such a model, even for
workmen who have had a long experience in escapements, our word for it
they will discover a great many new wrinkles they never dreamed of
previously.

It is important that every practical watchmaker should thoroughly master
the theory of the lever escapement and be able to comprehend and
understand at sight the faults and errors in such escapements, which, in
the every-day practice of his profession, come to his notice. In no
place is such knowledge more required than in fork and roller action. We
are led to say the above chiefly for the benefit of a class of workmen
who think there is a certain set of rules which, if they could be
obtained, would enable them to set to rights any and all escapements. It
is well to understand that no such system exists and that, practically,
we must make one error balance another; and it is the "know how" to make
such faults and errors counteract each other that enables one workman to
earn more for himself or his employer in two days than another workman,
who can file and drill as well as he can, will earn in a week.

PROPORTIONS OF THE DOUBLE-ROLLER ESCAPEMENT.

The proportion in size between the two rollers in a double-roller
escapement is an open question, or, at least, makers seldom agree on it.
Grossmann shows, in his work on the lever escapement, two sizes: (1)
Half the diameter of the acting roller; (2) two-thirds of the size of
the acting roller. The chief fault urged against a smaller safety roller
is, that it necessitates longer horns to the fork to carry out the
safety action. Longer horns mean more metal in the lever, and it is the
conceded policy of all recent makers to have the fork and pallets as
light as possible. Another fault pertaining to long horns is, when the
horn does have to act as safety action, a greater friction ensues.

In all soundly-constructed lever escapements the safety action is only
called