Chap. XT.

MECHANICS.

959

Danaide, Marquis Mannoury (TEdot ; this machine may be classed among hydraulicwheels; it consists of a cylindrical cistern of wood, dd, whose bottom is pierced in itscentre by a circular orifice r, through which passes a vertical iron axle p , retained above bya collar, and resting at its lower part on a pivot which allows it to turn on itself, drawingwith it the cistern to which it is firmly attached by means offour iron crosses, two of which, c, c, are shown in the section,and the two others dd, ee, in the section b ; this axle directedin the axis of the cistern does not completely close the centralorifice which it traverses. On the other hand it leaves aroundits circumference a circle through which the water can escapeby a circular diaphragm s fixed to the vertical axis p, and to thecrosses immediately below the latter : divide the cistern into twoequal parts, which cannot communicate with each other, exceptby the circle -which remains between the circular diaphragmand the inner surface of the cistern : the lower part cd,dc isdivided into eight cases by as many diaphragms, four ofwhich go from the axle p to the circumference, and thefour others do not touch the axle, so as not to obstruct theorifice r ; these diaphragms formed by plane surfaces descendfrom the circular diaphragm to the base of the cistern; thewater enters at the upper part of the cistern by the conduitpipe fc, which is bent conveniently to allow it to issue throughan orifice x in the form of steam, which strikes tangentially theconcave surface of this part through its whole height, puts thecistern in motion, descends to the lower part by the circle con-structed between the diaphragm s and the inner surface of the cistern, engages in thepartitions before indicated, and then issues through the orifice r to fall into the dischargepipe r. Such is the description and play of this machine, executed with the greatestsuccess in different manufactories ; an improvement was made in it, by substituting forthe diaphragm t with plane surfaces, others in a spiral form, prolonged to the upper edge n

of the cistern through the hollow crown in the centre ; the form given to these new

diaphragms allows the edge n to be suppressed, which prevents the water from spreadingbeyond ; by this modification the loss of active force is considerably diminished.

Machine of Cagniard Latour is composed of two cisterns, a and 5, the first filled

with water at the ordinary temperature, and the second with water at 75° centigrade;

in the first cistern is plunged an Archimedean screw C, in thesecond a bucket wheel d; a tube communicates the bottomof the first cistern with that of the second ; if we turn thescrew in a direction contrary to that necessary for elevating thewater contained in the cistern, it will cause the atmospheric airto descend, and following the direction of the tube of com-munication, will escape at the orifice e, the distance of whichfrom the cistern b should be less than that of the orifice rfrom the surface of the cistern c ; the cold air thus carried to thebottom of the cistern filled with hot water dilates, enters the buckets whose opening isturned downwards, and drives the wheel d. In the machine executed by Cagniard, theeffect produced consists of raising, by means of a cord attached to the axle of the wheel, aweight of 15 lbs. with a uniform vertical velocity of 1 inch per second, while the movingforce applied to the screw is only 3 lbs. with the same velocity : the effect of heat is toquintuple the natural effect of the moving power; the effect of the moving power beingquintupled, we may take from it a force with which to supply the moving power, andthere will then remain a disposable force of four times the moving power. The Archi-medean screw thus employed forms an excellent blowing engine.

A Gin , where a muffle is not employed, we obtain the ratio ofvelocities required but by substituting for the ordinary cylinderanother whose axle is composed of two parts, a and e , of differentdiameters; a cord, after being turned on the part a of the axle,passes through the movable pulley which supports the weightp , reascends and passes through another pulley, and i3 thenattached to the other part e of the cylinder, round which it isenveloped in a direction contrary to that in which it is woundround the part a ; by turning the cylinder the cord winds onthe part a while it unwinds from the part e, the power beingapplied at the extremity of the lever c. It may be easily con-ceived that at each turn of the cylinder, the weight d onlygoes over a space equal to half the differences of the two cir-cumferences of the cylinders a and e, a quantity which we may /render as small as we please.

Fig. 1343.

Fig. 1341.

Fig. 1344.