Chap. XVII.

OF THE MOTION OF FLUIDS.

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and the air from the vessel C or P pq Q escapes by the same opening : a tube An traversesthe cover P Q, and the bottom pq of the vessel C"; oil is poured through the orifice A ; itflows through the other orifice a, and falls into the vessel C or pq U; the air of the vesselescapes through the same orifice, of the tube A a, and as we suppose the cock Z closed, thevessel C is filled.

It does not suffice to till the two vessels C and C' ; ; we must empty the vessel C', thebottom of which communicates with a pipe V X closed by a plug ; we remove the plug andthe liquid runs out; but at the same time the air must introduce itself, which it does intwo ways, for it may enter by the tube IIel’ before we have filled the vessel C', or by thecup a&Se, which is closed by a plug Y removable at pleasure.

Fig. 1757. is the form which Girard presented to the Polytechnic School. Of the throelevels XI, ni, US, in the three vessels C, C', C", two being given, the third is found;knowing the volumes of these vessels, we find by calculation the relation between thequantities which determine the position of their level lines.

Description of the Hydraulic Ram . — The water from a source enters at A with anacquired velocity due to the height of the fall, flows through the conduit-pipe A 13, which

HYDRAULIC HAM

is exchanged at A, and inclined with a fall of at least 27 millimetres in 2 metres ; it escapesby an orifice C, which may be closed at pleasure by a valve. A reservoir of air, F, isunited by means of a cylindrical pipe, abed, to the conduit pipe, II D ; at the centre of thebottom of the reservoir F is a circular orifice, to which a small cylindrical support isadapted, whose extremity, E, is furnished with a valve; s is another valve destined to main-tain the air in the reservoir F, and in the space mn, comprised between the pipe abed, andthe small support E of the valve ; G III is an ascension pipe, which rises from G in theair reservoir F. The pipe A 15, 13 C, by which the water flows from the source, is calledthe bodv of the ram; the tube Gill, through which the water elevates itself above thesource, the ascension pipe; of the two valves D and E, which close the orifices C and E,the first is the flowing or stopping valve, and the second the ascension valve ; these valvesare hollow balls, D and E, which are retained by muzzles, and they do not weigh more thantwice the volume of water they displace ; the extremity of the body of the ram, which car-ries the valves and reservoir of air, F, is termed the head.

This machine acts in the following manner: the water through the orifice C acquires avelocity due to the height of the fall; it obliges the ball I) to leave its muzzle, and elevateitself to the orifice C, which is terminated by round pieces of leather, or tarred cloth, towhich the ball applies itself exactly ; as soon as the efflux through this orifice stops, thewater raises the ball E, which closes the orifice E of the air reservoir F, and flows at thesame time into this reservoir and into the ascension pipe G III. losing the velocity whichit had at the moment when the opening C was closed; the balls I) and E then fall by theirown weight, one into its muzzle, the other into the orifice E; the water from the sourcebegins again to flow through the orifice 0, the valve D again closes, and the same effectsare produced. The revolution of the ram continences when the stopping valve D ceases tobe applied to the orifice C ; it ends when this valve returns to the same position : in thisrevolution there are four distinct operations; in the first, the water, by flowing through theorifice C, acquires a part of the velocity due to the height ot the falls, and the stoppingvalve D closes ; in the second, the stopping and ascension valves are closed, and the elasticbodies, whether metals or air, are compressed ; in the third, the ascension valve opens theair of the reservoir F, which is compressed ; the water elevates itself in the- ascension pipeG, the ascension valve closes, and the stopping valve does not re-open ; in the fourth, theelastic bodies compressed in the second re-act, the ascension valve remains in its place, andthe stopping valve, no longer applied to the orifice C, falls into its muzzle. Y ith regardto the duration of time occupied by these four operations, we may observe that in the first,if the distance from the stopping valve D to the orifice C, and the weight of the valve, beincreased, the greater will be the velocity of the water which flows through the orifice C,to raise the valve D and apply it to the orifice C: for each position of the valve, at the

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