(continued from page 171) There are mainly two distinct plans adopted in the application of the Saw, when it is removed from the hands of the artizan or workman and intrusted to the guidance of rods or ??ulleys. Upright or reciprocating saw II)achines are largeiy employed to per. form that kind of sawing which was for ??er . Iy done at the saw pit, the larger Upflght sa ws are used tor cutting round or square t'mber into thick planks, the smaller for cutt :ng deals into boards. The framing of the earlier of these machines was mostly fo rmed of wood, a material which still prevails for this purpose in many districts, although the best are now made entirely ot iron. But the circular saw is ra pid ly gaining ground as a competitor over the straight saw, and is manufactured of as large a size as 6 feet in dia meter. Other fo rms ot this t{lol are s . ome. times used, although their em ployme nt IS not gene ral ; for instance, we . fin.d for many ??, mall articles, that several vanatIOns of the tre phine saw " are employed under the names. of crown annular, curvilinear, drum, c. Still , whate??er the nature of the work, it may be classed under one of three varieties, aceordi??g as the saw cuts the lengthway of the gram, across it, or in a curvilinear direction. Re verting to the uprigh t sa w machm.es, the lead. ing principles of their constructIOn . are ?ut slightly varied, the intended purpose IS to give an alternate vertical movement to the saws, whilst,at the same time, a slow progressive ??o. rizontal motion is imparted to the table whIch supports the timber to be sawn. For this pur pose two standards or upright beams support the guide bars down which the saw frame slides, while the frame itself is made sufficiently large to accommodate several saws, sometimes as many as eleven being employed, so that twelve boards can be produced from one plank. The frame keeps the blades straight, gives them tension, and enab??e?? the foree to be applied without the fisk of Injury. The distances between the blades are adjusted by interposing pieces of wood and pressing the whole together by side screws, after which the saws are separately tightened by steel wedges. To allow of this adjustment, the saws have buckles rivetted to them, and these generall y pass th rough mortices in the top and bottom rlUls of. the slid??ng frame. This latter has appropriate beanngs at the four angles: to fit the slide bars, and the alte rnate motion is given to it by a crank shaft ; th e conn ectin g rods are not attached directly to the saw frame, but to a cross head which is jointed at its centre to th e frame, so that ev??n supposing the two cranks to ???? a little dissimilar in length or angular posItIon . ' they nevertheless move the fr ame equally Without straining or rocking it. The advan tag.e of a long connecting rod entails the necessity. of allowing grea?? depth to the standa??ds w .hlch sometimes measure eighteen feet In height, and in order to bring the machiuery into more moderate compass, it is proposed to use a fork. ed connecting rod. The friction caused by th?? rapid motion ot the saw trame, IS very considerable, so that the guides require to be well adjusted. The timber lies on a bed which is placed on a series ot rollers, and IS made to advance towards the saws by means of a rack and pinion, which are actuated by a ratchet movement, so that Wl,en the reta inin g pawls are turned back a retrograd e motion can be given to the bed . Ib is possi ble to dis. pense with the long rack by graspi n g the tim. ber between two grooved feeding rollers, the one fixed to the fr am ing of the machine, the other pressed up by a loaded lever, and moved a smal l step at each time by a rat chet, as usual but this plan does not prevail . The balk is ' held in its right position by dogs, and in some machines, both these and the timber can be moved in transverse directions to suit the varying widths of the lumber. At the City of London Saw Mills the rna. chine for cuttin g lo gs or balks of timber into thin veneer planks; is very accurate-.in {lne instance,-a log of Honduras mahogany , .18 feet long and 3 feet 1 inch sq nare, was cut m. to unbroken sheets at the rate of ten to an inch, and so beautifully smooth as to require scarcely any dressing. ??oiPro"tin g ",w. ?? mo,h ??'" fu, '0,. 5citnfific vilinear works, such as bevelled timber fo. ship.building, felloes of wheels, circular ralls of chair backs, c. For these it is usual to have a narrow saw moving vertically, whilst the bed is capable of motion in various direc. tions. In som e cases the work can be guid e d by a fixed circula r fe nce or by radius bars; for bevelled works the table can be tilted to any angle, and for such adjustment it appears. I??referable to allow it to swing on a central .JOlUt. In other cases the saw frame is jointed and may be brought down by a swing fra ?? e in the arc of a circle, to penetrate to any aSSigned depth. Small reciprocating saw machines, fitted up as adjuncts to the lathe, are often found advantageous to mechanics using that tool a.nd occasionally cutting curved work. In one 1Ustance the saw is stretched in a frame about 4 to 6 inches high, and from 10 to 14 inches wide, a small pulley beneath the lathe. bearers recei ves continuous motion from the foot w heel, the end of a cord is fixed to the pulle at a small distance from the centre, the other end is passed beneath another small pulley, and carried on to the trame, which is forced upward by a spiral spring, and then pulled down by the cord. III other small machlDes the saw is unprovided with the frame, by w hi ch it is generall y s tretc hed an d g uide d, t hese J uucti ons bein g fulfilled by the motive par t of the apparatus, one instrument of this sort has a sprin g attached to each end of the saw and a small eccentric gives the mo:ion by fixi??g a loop of wire, which emhraces it, to the lower spring, so that when the eccentric revolves the s pr ing is thrown into rapid vibration, and with care in the arrangement the saw can be made to traverse very nearly throu"h the same point of the platform. These sman"saws are chiefly adapted for cabinetma kers and other s who re quire to cut thin curvilinear pieces. When the straight saw is used in cross cutting machines, it is customary to g ive the frame a horizontal recip ro cati ng and al s o a ve rti cal feeding moti on, and almost to counterp oise the weight, so t hat a moderate pressure only bears on the saw teeth. The forms ot the tee t h differ considerably, according to the nature of the work , a tOf)th of. ten used for cross-cutting is said to l:le of up right pitc h from p resentin g equal angles on each side, but another kind more generally employed for small cross cutting saws is in. clined about 15 fron: the last, this is termed slight pitch ; in ordinary pitch the face is per pend icula r and the back inclines at an angle of 300 from t he edge of the saw; this shape is likewise used for cutting metal, for circular sa ws when the work is fine, and often for cross: cut circular saws Some ti mes in mill saws for soft woods the face of the teeth is set forward , or s tretches bey o n d the perpendicular at an inclination of 15", n ea rly the same tooth is likewise ad a pted for ,circular Eaws, and cutters for metal. S ome teeth ar e called gulle t teeth , on account of the large hollow or gUllet that is cut away in front of each tooth in continuation of the face, they are also known as br iar teeth. The tooth is, in general, cut by one punch fill in g the entir e space. This s hape allows more room for the saw- dust, and is less disposed to retain it than the angular notch so that it is much employed,although the angles of the f??ce 2nd back are vaned according to the species of wood , for mahogany, rosewood and. other hard woods, and likewise for cross-cutting the angle of the face may be 900. and that of the back 300, for 89ft woods and ripping with the grain the angle should be less. (To be Continued.)