1192

THEORY AND PRACTICE OP ENGINEERING

Rook IE

cylinders, C, by means of iron rods B, and these drive six piston rods, F, on each side thewheel; each system of pumps is contained in a trough, and firmly secured by screwsto two joints pierced with holes to admit the water of the canal. The three branches ofeach system unite in the forks O, O which convey the water to the discharging pipe P ; thepumps are tied together by interties, to which they are secured by iron bands; thedepth of water near the fall at Q is 2 feet, and it has that velocity per second, as it runsalong an inclined plane whose height is 10 feet: to find the absolute force of the current onthe float-board, find a mean proportional between 2 and 12, which is 4 feet 10^, inches, cor-responding to the tabular velocity of 17 feet Thus the absolute power may be re-

garded as equivalent to the weight of a column of water having the superficies of the floatsfor its base, and a height of 4 feet 10-^j inches ; the diameter of the wheel is 24 feet, itsfloat-boards are 5 feet long by 1 high ; consequently the absolute power is equivalent to aweight of 1715 pounds.

The cranks are 1 foot in diameter, and so arranged that when one is horizontal the otheris vertical : by this means the pistons of one only of the four systems force at the same time,by the action of a power which is only -j* 2 part of the weight of the three columns of watersustained by these pistons, the radius of the crank being that of the wheel. The diameterof the pump-barrels is 10 feet, and that of their branch 3; thus its circle will only beexpressed by 9, while that of the pistons will be 100, a defect common to all forcing-pumps,and which is considerable in the present instance, on account of the bends in the brancheswhich prevent the water from rising, and consequently require a greater amount of powerthan is possessed by thpse pumps. As this increase cannot take place without augment-ing the velocity of the current, and that of the wheel does not diminish in proportion, theproduct of the machine will be much less than it naturally ought to be; in other respectsit is simple and well contrived.

Fig. 1846. is a machine for working forcing-pumps, executed at Val St. Pierre, Giartreuse,in Tierache, 2 leagues from Vervins : it was formerly only supplied by drawing water froma deep well, until 1720,when the book of Che-valier Morland havingfallen into the handsof Don Fougeres, thenPrior, he seized the ideaof that author on thesubject of ellipses, whichhe proposed to use inplace of the crank to workpmnps, and applied themto a machine driven bya horse to raise waterfrom a well to a heightof 150-feet. Hie ma-chine consists of a turn-ing post I, carrying acogwheel, which engages a lantern, whose axle carries three equal and similarellipses N, in whose circumference is a channel similar to that of a pulley ; these ellipsesare so placed, that if brought together the extremities of their greater axes wouldform the six angles of a regular hexagon. O is a post in whose summit are threeslits, through which pass as many balance beams P, S, traversed by a bolt servingas a common axis ; to keep them in the same direction they are maintained by frames,T V, attached to a joist : one of the extremities of each beam is held by two braces,8, Q, between which are rollers R, which work in the channels of the ellipses; at theother extremity X are suspended the rods X Y, of three pump-barrels, placed in asmall vault, to which they are attached by iron cramps. The branches pass from the pumpbarrels through the vault to the reservoir by an inclined plane of 1200 feet. To understandthe play of this machine, suppose the horse attached to the swing trees and having hishalter attached to the guide bar; when he advances, he turns the wheel and lantern M, andconsequently the ellipses which move the balance beams by the difference of their axis; forwhen the great axis is vertical, the centre of the rollers is raised to a height equal to half thedifference between the greater and lesser axis; when this axis becomes horizontal, it descendsthe same quantity : thus each roller goes over half the circumference of an ellipsis, andduring each revolution the piston sucks and forces twice, the rollers never quitting theirchannel, because the part O Q of the balance beams bears by its length and weight on theresistance of the other part PO: each ellipse may be regarded as the union of fourinclined and curvilinear planes turning round a fixed point, and at each revolution aplane compels the weight to ascend from the foot to the summit; a second succeeds, downwhich the weight descends by its own gravity; it then rises up the third, and falls down the

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