thickness with the required boards or leaves; the whole is then pressed together and held in position by packing screws. The saws themselves are subsequently tightened by forcing home the keys until a certain amount of tension has been attained, this is ascertained only by the peculiar sound which emanates from the blade on being drawn considerably tight and tense. Great experience is required to accustom the ear to the correct intonation, as in general the tensile strain on the saws approximates so closely to the breaking point that one or two extra taps on the keys are quite sufficient to rupture them. Mr. Brunel, in the government saw-mills at Woolwich, adopted a method of hanging saws by means of a weighted lever, like a Roman steelyard. A cross-shaft affixed above the saws to the cornice of the main frame carried a lever, weighted at one end and provided with a hook or shackle at the other for engagement with the saw buckle. In using this apparatus the blades were strained one at a time by linking the lever to the buckle and then adjusting the movable weight until the desired tension was acquired, after which the key was inserted into the mortise and the lever released. This arrangement is not now in common use on account of the trouble attending its employment, and at present the saws are merely strained by hammering up the keys. The saw blades had usually a tensile strain of upwards of one tun per inch of breadth of blade. It is to be further observed that the cutting edges of the saws are not quite perpendicular, but have a little lead, or their upper ends overhang the lower about three eighths of an inch or one half of an inch, according to the nature of the material to be sawn. The object of this is that the saws may be withdrawn from the cuts in the ascending or back stroke, and allow the sawdust free escape. The eccentric actuating the mechanism for advancing the timber to the saws is generally set in such a manner that the feed commences just at the moment when the frame has attained half its ascending stroke, and continues until the entire stroke has been completed. By this regulation the saws are not liable to be suddenly choked, but come smoothly and softly into their work.--_Worssam's Mechanical Saws_. * * * * * PATENT DECISION.