The revolution of the spindles at a speed suitable for winding the
threads upon the spindles as the carriage moves inwards. (3) The guiding
of the threads upon the spindles in such a manner that a cop of yarn
will eventually be formed upon each spindle, of such dimensions and
shape as to be quite suitable for any subsequent processes or handling.

Taking these three important divisions in the order given, it may be
said that the drawing-in of the carriage is effected through the medium
of the "scroll" bands, which are attached to the carriage at one end,
and to certain spiral scrolls or fusees at the other end. The scrolls
being revolved, wind the cords or bands round them, so pulling in the
carriage. There are usually two back scroll bands and one front band,
the latter being a sort of check band upon the action of the other two.
What is termed the "rim band" revolves the spindles during the outward
traverse of the carriage.

The drawing-in of the carriage in a sense causes the other two
operations to be performed. With respect to the second of these, viz.,
revolving the spindles and thus winding the threads upon them, it may be
said this action causes what is termed the "Winding Chain" to pull off a
small drum of six inches diameter, thus rotating the latter and thereby
the spindles. Here, however, comes in now the action of the very
beautiful and effective piece of mechanism, "Roberts' quadrant" (see
Fig. 26). The winding chain just mentioned is attached to one extremity
to the arm of the quadrant, and the peculiar manner in which the
quadrant moves in relation to the winding drum gives the variable motion
to the spindles that is required.

When commencing a new set of cops it may take about eighty revolutions
of the spindles to wind on the 64 inches of thread to each spindle,
representing one stretch. The bare spindle may be about a quarter of an
inch in diameter, but it may finally attain a diameter of an inch and a
quarter (_i.e._, the cop upon the spindle). This cop will only require
about twenty revolutions to wind on the 64 inches, which are only
one-fourth of the revolutions necessary for the empty spindles. It is
the action of the quadrant which gives this variation in speed to the
spindles during winding-on.

But as has been pointed out previously, the quadrant imparts a
"differential winding" motion to the spindles in two distinct and
different ways, and the second motion is even more important than the