All or any part of the machinery which we have described may be driven by the power of steam, water, wind, or animals. In the course of describing the different machines, and their component parts, adapted for the various purposes of the invention, we have seldom taken notice either of their dimensions or of the materials of which they may be made, because no fixed rules can be given: but any competent mechanic, from what we have shown, will be enabled to apply such sizes, and use such materials, as may be suited and proportioned to the nature and design of each machine, and to the power which is to drive it, particularly when we add, that the figures in the plates marked "Tempering, Tempering, and Backward and Forward Movements,' are made out on a scale of an inch to a foot, and that the dimensions there given are such as inay with effect be applied in practice.

SAW-MILLS.

SAW-MILLS, constructed for the purpose of sawing either timber or stone, are moved by animals, by water, by wind, or by steam. They may be distinguished into two kinds; those in which the motion of the saw is reciprocating, and those in which the saws have a rotatory motion. In either case the researches of theorists have not yet turned to any account: instead therefore of giving any uncertain theory here, we shall proceed to the descriptive part, and refer those who wish to see some curious investigations on this subject to a Memoir on the Action of Saws, by Euler, en Mem. Acad. Roy. Berlin, 1756.

Reciprocating saw-mills, for cutting timber, and moved by water, do not exhibit much variety in their construction. The saw-mill represented in fig. 450 is taken from Gray's Experienced Mill-wright; but it only differs in a few trifling particulars, from some which are described in Belidor's Architecture Hydraulique, and in Gallon's Collection of Machines approved by the French Academy.

The plate just referred to shows the elevation of the mill. A A the shaft or axle upon which is fixed the wheel B B, (of 174 or 18 feet diameter,) containing 40 buckets to receive the water which impels it round C C, a wheel upon the same shaft containing 96 teeth, to drive the pinion No. 2, having 22 teeth, which is fastened upon an iron axle or spindle, having a couplingbox on each end that turns the cranks, as D D, round; one end of the pole E is put on the crank, and its other end moves on a joint or iron bolt at F, in the lower end of the frame G G. The crank D D, being turned round in the pole E, moves the frames G G up and down, and those having saws in them, by this motion cut the wood. The pinion No. 2 may work two,

three, or more cranks, and thus move as many frames of saws. No. 3 an iron wheel having angular teeth, which one end of the iron K takes hold of, while its other end rolls on a bolt in the lever H H. One end of this lever moves on a bolt at I, the other end may lay in a notch in the frame G G so as to be pulled up and down by it. Thus the catch K pulls the wheel round, while the catch I falls into the teeth and prevents it from going backwards.

Upon the axle of No. 3 is also fixed the pinion No. 4 taking into the teeth in the under edge of the iron bar, that is fastened upon the frame TT, on which the wood to be cut is laid: by this means the frame TT is moved on its rollers SS, along the fixed frame U U ; and of course the wood fastened upon it is brought forward to the saws as they are moved up and down by reason of the turning of the crank DD. VV the machine and handle to raise the sluice, when the water is to be let upon the wheel B B, to give it motion. By pulling the rope at the longer arm of the lever M, the pinion No. 2 is put into the hold or gripe of the wheel C C, which drives it; and by pulling the rope R, this pinion is cleared from the wheel. No. 5, a pinion containing 24 teeth, driven by the wheel C C, and having upon its axle a sheave, on which is the rope P P, passing to the sheave No. 6, to turn it round; and upon its axle is fixed the pinion No.7, acting on the teeth in an iron bar upon the frame TT, to roll that frame backwards when empty. By pull ing the rope at the longer arm of the lever N, the pinion No. 5 is put into the hold of the wheel C C; and by pulling the rope O, it is taken off the hold. No. 8, a wheel fixed upon the axle No. 9, having upon its periphery angular teeth, into which the catch No. 10 takes, and being moved by the lever attached to the upper part of the frame G, it pushes the wheel No. 8 round; and the catch, No. 11, falls into the teeth of the wheel, to prevent it from going backward, while the rope rolls in its axle, and drags the logs or pieces of wood in at the door Y, to be laid upon the movable frames TT, and carried forward to the saws to be cut. The catches Nos. 10 and 11 are easily thrown out of play when they are not wanted. The gudgeons in the shafts, rounds of the cranks, spindles, and pivots, should all turn round in cods or bushes of brass. Z, a door in one end of the mill-house at which the wood is conveyed out when cut. W W, walls of the mill-house. QQ, the couples or framing of the roof, X X X, &c. windows to admit light to the house.

Saw-mills for cutting blocks of stone are generally, though not always, moved horizontally; the horizontal alternate motion may be commu nicated to one or more saws, by means of a rotatory motion, either by the use of cranks, &c. or in some such way as the following. Let the borizontal wheel A B D C, fig. 451, drive the pinion O N, this latter carrying a vertical pin P, at the distance of about one-third of the diameter from the centre. This pinion and pin are represented separately in No. 2 of fig. 451. Let the frame W STV, carrying four saws, marked 1, 2, 3, 4, have wheels, V, T, W, W, each running in a groove or reel, whose direction is parallel to the proposed direction of the saws: and let a transverse groove PR, whose length is double the distance of the pin P from the centre of the pinion, be cut in the saw-frame to receive that pin. Then, as the great wheel revolves, it drives the pinion, and carries round the pin P; and this pin being compelled to slide in the straight groove PR, while by the rotation of the pinion on which it is fixed its distance from the great wheel is constantly varying, it causes the whole saw frame to approach and recede from the great wheel alternately, while the grooves in which the wheels run confine the frame, so as to move in the direction Tt, Vv. Other blocks may be sawn at the same time by the motion of the great wheel, if other pinions and frames running off in the directions of the respective radii, E B, E A, E C, be

worked by the teeth at the quadrantal points B A and C. And the contrary efforts of these four frames and pinions, will tend to soften down the jolts, and equalize the whole motion.

The same contrivance, of a pin fixed at a suitable distance from the centre of a wheel, and sliding in a groove, may serve to convert a reciprocating into a rotatory motion; but it will not be preferable to the common conversion by means of a crank.

When saws are used to cut blocks of stone into pieces having cylindrical surfaces, a small addition is made to the apparatus. See figs. 452 and 453. The saw, instead of being allowed to fall in a vertical groove, as it cuts the block, is attached to a lever or beam F G, sufficiently strong; this lever has several holes pierced through it, and so has the vertical piece E D, which is likewise movable towards either side of the frame in grooves in the top and bottom pieces A L, D M. Thus the length K G of the radius can be varied at pleasure, to suit the curvature N ; and as the saw is moved backwards and forwards by proper machinery, in the direction C B, BC, it works lower and lower into the block, while, being confined by the beam FG, it cuts the cylindrical portion from the block P, as required.

When a complete cylindrical pillar is to be cut out of one block of stone, the first thing will be to ascertain in the block the position of the axis of the cylinder; then lay the block so that such axis shall be parallel to the horizon, and let a cylindrical hole of from one to three inches diameter be bored entirely through it. Let an iron-bar, whose diameter is rather less than that of the tube, be put through it, having just room to slide freely to and fro as occasion may require. Each end of this bar should terminate in a screw, on which a nut and frame may be fastened; the nut-frame should carry three flat pieces of wood or iron, each having a slit running along its middle nearly from one end to the other, and a screw and handle must be adapted to each slit: by these means the frame work at each end of the bars may readily be so adjusted as to form isosceles or equilateral triangles; the iron-bar will connect two corresponding angles of these triangles; the saw to be used, two other corresponding angles; and another box of iron or of wood, the two remaining angles; to give sufficient strength to the whole frame. This construction, it is obvious, will enable the workman to place the saw at any proposed distance from the hole drilled through the middle of the block; and then, by giving the alternating motion to the sawframe, the cylinder may at length be cut from the block as required. This method was first described in the Collection of Machines approved by the Paris Academy.

If it were proposed to saw a conic frustrum from such a block, then let two frames of wood or iron be fixed to those parallel ends of the block which are intended to coincide with the bases of the frustrum, circular grooves being previously cut in these frames to correspond with the circum