nds them
upon tubes. This machine is usually the last employed to prepare
cotton for spinning, but for spinning fine yarns from the best
Egyptian and Sea Islands cottons, a second roving, or _Jack frame_ may
be required, in which event pairs of rovings from the first machine
are similarly treated in the second in order to render the final
product sufficiently fine for spinning yarns of the requisite counts.

_Spinning_ (see SPINNING).--Improvements upon the Saxony wheel caused
continuous spinning to become a mechanical art at an earlier date than
intermittent spinning. Arkwright's water-twist frame was gradually
changed to the _throstle_, which was a duplex machine furnished with
one set of drawing rollers, and one set of spindles and flyers at each
side of the frame-work. All the bosses of one line of rollers were
connected so that one driving gear would serve for the whole length,
and all the spindles were driven by bands from a central cylinder. The
roving spools were placed vertically in a creel between the two sets
of rollers, and the rovings reduced to the requisite fineness by the
latter; after which each was passed through a coiled eye at the lower
end of a flyer leg, and attached to a double-flanged spool which was
loosely mounted upon a spindle. At each revolution of a flyer a twist
was put into the attenuated roving, and the flyer wrapped as much
thread upon a spool as the rollers delivered. The spools rested upon a
piece of woollen cloth stretched over a rail, and this rail rose and
fell through a space equal to the length of the spool barrel. On
account of a thread having to pull a spool round, it was not possible
to spin finer counts than 60^s, and since each flyer was mounted upon
the top of an unsupported spindle, vibration increased with speed. In
order to avoid such vibration Mr Danforth, in or about 1829, placed an
inverted cup upon the top of a stationary spindle, and upon the
spindle a freely fitting sleeve and wharve; the former to receive a
spool, the latter to rotate both. By a traverse motion all the spools
were simultaneously raised or depressed, so as to have their barrels,
when at the highest point, entirely within the cup, and when at the
lowest entirely below it. A thread passed from the drawing rollers,
outside the cup, to a spool. As a spool rotated its thread was
uniformly twisted, the lower edge of the cup built the ya