t stones
to perfectly perform their functions will take but a few minutes. In
fact, if the stones will answer at all, three to five minutes is as much
time as one could well devote to the adjustment. The reader will see
that if the lever is properly banked all he has to do is to set the
stones so the lock, draw and drop are right, when the entire escapement
is as it should be, and will need no further trial or manipulating.

CHAPTER II.

THE CYLINDER ESCAPEMENT.

There is always in mechanical matters an underlying combination of
principles and relations of parts known as "theory." We often hear the
remark made that such a thing may be all right in theory, but will not
work in practice. This statement has no foundation in fact. If a given
mechanical device accords strictly with theory, it will come out all
right practically. _Mental conceptions_ of a machine are what we may
term their theoretical existence.

When we make drawings of a machine mentally conceived, we commence its
mechanical construction, and if we make such drawings to scale, and add
a specification stating the materials to be employed, we leave only the
merest mechanical details to be carried out; the brain work is done and
only finger work remains to be executed.

With these preliminary remarks we will take up the consideration of the
cylinder escapement invented by Robert Graham about the year 1720. It is
one of the two so-called frictional rest dead-beat escapements which
have come into popular use, the other being the duplex. Usage, or, to
put it in other words, experience derived from the actual manufacture of
the cylinder escapement, settled the best forms and proportions of the
several parts years ago. Still, makers vary slightly on certain lines,
which are important for a man who repairs such watches to know and be
able to carry out, in order to put them in a condition to perform as
intended by the manufacturers. It is not knowing these lines which
leaves the average watchmaker so much at sea. He cuts and moves and
shifts parts about to see if dumb luck will not supply the correction he
does not know how to make. This requisite knowledge does not consist so
much in knowing how to file or grind as it does in discriminating where
such application of manual dexterity is to be applied. And right here
let us make a remark to which we will call attention again later on. The
point of this remark lies in the question--How many of the so-calle