Before flax can be converted into cloth or other articles, it undergoes certain preparatory processes, constituting what is called " dressing;" the object of which is to separate the boon, or core, from the flax, which is the cuticle, or bark of the plant, and to straighten out the fibres for the spinner. These operations are sometimes performed by hand, but at the present day more commonly by machinery, driven by steam or water power. When the flax is dressed by hand, the bark is separated from the core by means of an instrument called a "flax-brake," composed of three wooden teeth or swords, fastened longitudinally on a horizontal bench, and of a lever, to the under side of which are fixed similar, but rather smaller teeth, which fit in between the interstices of the others. The flax being held in the left hand across the under swords of the brake, the upper teeth are then with the right hand quickly and often forced down upon the flax, which is artfully shifted and turned with the left hand, in order that it may be fully and completely broken in its whole length.

The fibres are then straightened by means of a kind of comb called a " hackle," whence the operation is termed " hackling." The hackle is composed of a number of long teeth or spikes, fixed firmly in a bench; and the workman striking the flax upon the teeth, draws it quickly through them. To persons unacquainted with this kind of work it may seem a very simple kind of operation; but, in fact, it requires as much practice to hackle well as any other operation in the whole manufacture of linen. The workmen use finer, or coarser, and wider-teethed hackles, according to the quality of the flax; generally putting the flax through two hackles, a coarser one at first, and then a finer one in finishing it. But the hand methods of breaking and scotching of flax are, however, too tedious in their operation to give satisfaction to the manufacturers in the present advanced state of mechanical science, and accordingly mills have been constructed by which these preparatory operations are much facilitated. These mills differ greatly in their form, and the mode of their operation.

A very simple and efficient one is described in Gray's Experienced Millwright, and is constructed as follows: - Upon the main shaft, or axis of a water-wheel, is fixed a large bevilled wheel, which turns three horizontal fluted or toothed rollers, by means of a pinion on the axis of the middle one, the upper and lower rollers being kept pressed against the lower one by weighted lever?, and being carried round by contact with it. The driving-wheel likewise gives motion to an upright shaft, by means of a small pinion fixed upon the foot of the shaft; upon the upper part of this shaft are fixed cross arms, to which are attached scotches, revolving within a cylindrical casing. The rough flax is made up into small parcels, which being introduced between the middle and upper rollers, pass round the middle one, and this, either having rollers placed on its off side, or being enclosed by a curved board, turns the flax out between the middle and under rollers, when the flax is again put in between the middle and upper one, and passes round the same course until it be sufficiently broken or softened, and prepared for the scotching machine.

The scotches, as before stated, are inclosed in a cylindrical casing; in the periphery of this casing are a number of apertures, and at these holes a handful of flax being held, the revolving scotches clear off" the refuse.