COTTON MANUFACTURE. 83 
attenuation of the riband; this inconvenience is obviated by the simple 
expedient of uniting together several of the formerly drawn slivers at each 
repeated drawing. This operation is called doubling, and insures this 
advantage, that the uneven portions of the slivers mutually correct each 
other, and finally a uniform riband results. 
3. Tae Rovine FRAME. 
The next operation after the above-described process of drawing is the 
preparation of the roving, which is a thin sliver with a slight twist. In the 
tube-roving frame this twist is only momentary. In this stage of the cotton 
manufacture the greatest care is necessary to preserve the uniformity of the 
spongy cord, upon which the evenness of the yarn depends. Since the first 
can-roving frame, invented by Arkwright, numberless machines have been 
contrived for performing this operation with exactness. In Arkwright’s 
machine the slivers, after passing through the ordinary drawing-rollers, 
received a slight twist by the revolution of the tin cans into which the 
roving fell, and around the interior surface of which they were regularly 
coiled by the centrifugal force. This machine is in fact the ordinary draw- 
ing-frame (pl. 17, jig. 17), with the receiving-can revolving on a pivot. 
This frame, though effective in the hands of its inventor, was still defective ; 
the torsion was unequal upon different portions of the yarn, and even when 
the twist was put in it was liable to be deranged as it was drawn from 
the cans. 
A machine constructed upon the principle of the common spinning-wheel 
is in very common use for the preparation of the rovings. The difficulty 
with these machines arises from the soft and delicate nature of the roving 
and the care necessary to regulate the winding-on, that it be neither slower 
nor faster than the delivery from the front rollers. The care required was 
increased by the constantly varying size of the bobbin within the flyer, as 
successive layers of roving were wound upon it, as well as by the changes 
occasionally required in the degree of twist to be given to the roving for 
particular purposes. 
The operation of this machine, called the bobbin-and-fly frame, is two- 
fold, twisting and winding. The twisting is accomplished by the revolution 
of the spindle, F (jigs. 21 a and 215), to which the fly-fork is united, whilst 
the sliver, A, in its progress from the rollers to the bobbin, passes through 
the hollow arm, u, which being made in one piece with the spindle, revolves 
_ with it. 
The amount of twist given to the roving depends upon the relative sur- 
face velocities of the drawing-rollers and the bobbin. 
The winding-on is accomplished by giving such a velocity to the bobbin 
that the difference between the motion of the surface of the bobbin and the 
motion of the delivering end of the flyer-arm is equal to the surface motion 
of the roller supplying the sliver. 
The first on the list of machines of this class is the tube-roving frame of 
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