automatic reeling machine this stretch is obtained by causing the
thread to take a turn round a pulley of a given winding speed, and
then, after leaving this pulley, to take a turn around a second pulley
having a somewhat greater winding speed.

[Illustration: Fig. 1 THE MECHANICAL REELING OF SILK.]

By this means the thread which is passing from one pulley to the other
is stretched by an amount equal to the difference of the winding speed
of the two pulleys. In the diagram (Fig. 2) the thread passes, as
shown by the arrows, over the pulley, P, and then over the pulley, P¹,
the latter having a slightly greater winding speed. Between these
pulleys it passes over the guide pulley, G. This latter is supported
by a lever hinged at S, and movable between the stops, TT¹. W is an
adjustable counterweight. When the thread is passed over the pulleys
and guided in this manner, the stretch to which it is subjected tends
to raise the guide and lever, so that the latter will be drawn up
against the stop, T¹, when the thread is so coarse that the effort
required to stretch it is sufficient to overcome the weight of the
guide pulley and the adjustable counterweight. But as the thread
becomes finer, which, in the case of reeling silk, happens either from
the tapering of the filaments or the dropping off of a cocoon, a
moment arrives when it is no longer strong enough to keep up the lever
and counterweight. These then descend, and the lever touches the lower
stop, T. It will be readily seen that the up and down movements of the
lever can be made to take place when the thread has reached any
desired maximum or minimum of size, the limits being fixed by suitably
adjusting the counterweight.

[Illustration: FIG. 2.]