Chap. XI.

MECHANICS.

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Fig. 1485.

t ig. I486.

Fig. 1487.

I'ig. 1485. Camus describesmachines which he has inventedfor making several sieves go atonce; that which the figure re-presents reduces itself to a greattable a; above this table is aplank be, sustained by two ironaxles n,n , which turn on two sup-ports of the same metal; these supports being fixed to the tableon the prolongation of one of the axles, or on a rod, which isin their direction on the plank, is fixed the pendulum rs, andconsequently communicates also an alternate circular motionto the plank be; its edges strike against the table a at eachoscillation, and imitate the vibrations or strikes which workmengive to sieves.

Fig. 1486. The cord a be is attached at a to the spring d,turns round the cylinder e, and is fixed at the extremity c ofthe pedal g. The circular alternate motion of the pedal com-municates another of the same nature to the cylinder e.

Fig. 1487. The circular alternate motion of the pedal dproduces circular continuous in the fly m, and circular alternatein the cylinder a.

Fig. 1488. Nippers for cutting off the heads of piles : theseconsist of two pieces of iron, abcd,efgh , which turn round theaxle i, the extremities ab, cf of these two pieces are cut into asemicircular form, in order the better to attach themselves tothe pile to be cut off, and their whole forms the beak of thenippers. The other extremities bcd,fgh of these same piecesof iron are terminated in two portions of arcs of circles, dc,gh,the first furnished with teeth in its convex, the other in its con-cave part: at the half of the interval which separates the twoares of circles, dc and gh, an axle s rises perpendicular to theplane of the nippers j this axle carries two pinions, n,m, whichengage, the first with the teeth of the arc dc, and the secondwith the teeth of the arc gh ; the circular alternate motion ofthe axle s will open or shut at pleasure the beak of the nippers.

Fig. 1489. A long bar or beam ab is traversed in its centreby an axle which is at the upper extremity of an upright postcd. The circular alternate motion communicated to one ofthe extremities of the bar a b by the action of a person seatedat this point, and who tends alternately, sometimes to elevatehimself by forcing his feet against the pavement, sometimes todescend by his own weight, communicates the same motion toanother person seated at the opposite extremity.

Circular alternate motion with a uniform velocity , or variableaccording to a given law, may be transformed into alternate in agiven curve, with a velocity of the same nature as that of themotion which produces it, constant or variable according to a given law in the same plane, or indifferent planes.

Fig. 1490. Lathe without an axle for making all sorts of screws, invented by Grandjean.This lathe is composed like common ones of a bench and two puppets, p, o ; these puppetshave, instead of points, two collars, s,t, to receive theaxle/^, terminated in a point at its twoextremities; this axle carries the piece r required to be turned,and the pulley g which receives the cord go attached to thetreadle o; the puppet a carries an iron support, *, to which isattached at i an iron square hik, one extremity of which leanson the point h of the axle, which it tends consequently to pressfrom h to f; the other extremity leans on a piece e, movableon an axle d, at the extremity d of which the piece dc ismounted on a square, in the groove of which slides a box d , towhich is attached the cord no, which is fastened to the treadleo; it is evident that by leaning the foot on the treadle we notonly shall turn the axle fh, but also lower the piece dc, whichcauses the axle to advance from f to h, by a quantity recipro-cally proportionate to the distance dn of the box n to the centred of motion; and as the piece n is movable, we may place it

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Fig. MSS.

Fig. 1189.

Fig 1490.