And its Modifications.

373

Chap. l.j

tube would become filled, and a jet of water would then be thrown fromthe upper orifice at every stroke. This efFect obviously depends upon therapidity with which the Instrument is worked, i. c. a sufficient velocitymust be given to the water by the upward stroke to prevent it descend-ing, tili the tube again reaches the lowest point, and consequently receivesanother supply of water. The Instrument should be straight and the boresmooth and uniform, that the liquid may glide through with the least pos-sible obstruction. As its length must be equal to the elevation to whichthe water is to be raised, it is necessarily of limited application, and espe-cially so since the whole (both water and apparatus) has to be lifted atevery stroke—not merely the liquid that is discharged, but the wholecontents of the machine.

By making the upper part of the tube slide witbin another that is fixed,a short part only of the apparatus might then be moved, and by connect-ing an air chamber as in No. 171, a continual stream from the dischargingorifice might be produced. A stuffing box should be adapted to the endof the fixed tube. Hachette suggested the application of a spring pole(like those used in old lathes) to communicate the quick reciprocating mo-tion which these machines require.

No. 172 represents another form of the instrument. Two spiral tubescoiled round in opposite directions are secured to and moved by a verti-cal shaft. Their upper ends are United and terminate in one dischargingorifice; the lower ones are enlarged, and each has a valve or clackopening inwards to retain the water that enters. By means of the handleA, which is mortised to the shaft, an alternating circular motion is im-parted to the whole, and the water thereby raised through these coiledtubes on precisely the same principle as through the perpendicular onesjust described. Thus, when the handle is moved either to the right handor to the left, one valve closes, and the water within receives an impulsethat continues its motion along the tube after the movement of the latteris reversed; and by the time its momentum is expended a fresh portionof water has entered that prevents its return. In this manner all the coilsbecome filled, and then every additional supply that enters below drivesbefore it an equal portion from the orifice above. This machine, there-fore differs from Nos. 170 and 171 only, in being adapted to a horizon-tal instead of a perpendicular movement. Each tube in the figure formsa distinct machine, and should be considered without reference to the other.Their discharging orifices are United to show how a constant jet may beproduced. By making the upper part turn in a stuffing box in the bottomof a fixed tube, as in No. 171, water might then be raised higher than themovable part of the apparatus.

That property by which all bodies tend to continue either in a state ofrest or motion, viz : inertia, increases the effect of these machines, for whenthe momentum imparted to the liquid in the tubes is exhausted, inertiaalone prevents it from instantaneously flowing back, and hence there istime for an additional portion of water to enter at the valve. The actionof the eanne hydraulique is similar to that by which persons throw waterto a distance from a bücket, or a wash-basin. The momentum given tothese vessels and their contents carries the latter to a distance, while theformer are held back or retained in the hands. Coals are thus thrown froma scuttle, earth from a shovel, and it is the same when a traveler on agalloping horse, or when drawn furiously in an open carriage, continueson his journey after the animal suddenly stops—his adhesion to his Seat,not being sufficient to resist the motal inertia of his body.