MILLS, saw, though extremely simple in their parts, require the greatest care in their formation. The saws, which are moved by cranks (much the same as those in use for pumps in water works), must be set with most scrupulous exact ness, else they will not only tear oblique ly, and destroy much wood, but create such an accumulation of friction, as must deteriorate the powers oCthe machine so as to approach the•equilibriuni. In most instances, the timber is brought forward to the saw by means of a small toothed wheel, and an axle, whereon the rope that pulls the timber is gradually coiled. See SAW-MILL.
Mute, flax, are generally worked by cattle ; their construction is simple; the essential parts being the hackle, which combs the flax ; and the scutcher, which strikes it: both tend to clearing away the coarser and unequal fibres, and to prepare the material for being spun, ei ther by hand, or by means of machinery.
We feel some surprise at the neglect shewn towards a very ingenious and use ful invention in the department of mill work ; vi:. the action of wheels, mutu ally, without the aid of cogs, or teeth. We have instances of wheels having been worked for nearly 30 years, simply by means of contact; the fellies (or cir cumference) being made of pieces of wood, having their grain, or fibres, all pointing to the centre. This produces a certain degree of roughness, exteriorly, which causes two wheels, thus formed, to bind sufficiently for the purposes of communicating rotation, where the stress is not excessive ; and even in that case, much may be effected by causing the wheels to bear very hard against each other, so as to excite friction to such an extent as may overcome the resistance of the weight, &c. We have seen a spin
ning machine consisting only of a vertical wheel (turned by a foot-lathe), that had its perimeter armed with a band of stout buff-leather ; which coming in contact with a number of bobbins, &c. caused all to move with great rapidity. Each bobbin was under the care of a little girl, who, by means of a slider, could either set it to work by approximation to the wheel, or liberate it from agency by withdrawing it from contact.
Having said thus much on the subject of mill-work, we beg leave to refer those of our readers, who may be in search of abstruse knowledge, to Olinthus Grego ry's work on the Theory of Mechanics; and to the excellent practical treatise of the late Mr. Smeaton, for a great variety of experiments, not only in this, but in many other most important branches of mechanics; which the limits of our vo lumes do not permit us to enter upon in any other than a brief, summary, and po pular manner.