1162

THEORY AND PRACTICE OF ENGINEERING.

Book I f.

atmospheric pressure elevates the water in the well by the suction pipe : the height towhich the water rises depends on the velocity with which it Hows from the source throughthe orifice K: the object of the dilated air reservoir IIII is to maintain the motion of theascending column G' G.

*0 Q

Tig. 17C0.

SUCTION RAM.

W e must now refer to what was before said on the return of the water, which the body ofthe ram contained, towards its source, and we shall easily conceive how this may become asuction ram: if the space mn, (fig. 1758.) of the bed of air communicates by a tube withthe reservoir of water placed below the body of the ram, at each re-action of the bed of airthe water of the reservoir would elevate itself, to equalise the elastic force of the air con-tained in the space mn and the atmospheric air ; and if the distance of the lower reservoirfrom the body of the ram is not too considerable, the water of this reservoir would flowwith the water ot the source which puts the ram in motion : when we estimate the totaleffect of the ram, we must then have regard both to the water elevated by the ascensionpipe and that elevated by the return of the ram.

Example of this double Effect. — Montgolfier had placed a ram’s head at the extremity ofa cast-iron pipe 54 millimetres (2 inches) in diameter, and 19*5 metres (60 feet) in length ;this tube expended 65 litres of water per minute, falling from 3*25 metres (lOfeet); takingfor unity a cube decimetre or litre of water elevated 1 decimetre, the power expended in aminute by the body of the ram was 2212. At each pulsation of the active column of theram, which was followed by the return of the flowing valve to its orifice, 142*44 cube centi-metres of water were elevated by the ascension tube 18*516 metres, the interval betweenthe two pulsations being 1 second; the ascension tube furnished 8*546 litres of water in aminute to a vertical height of 18*516 metres; thus the force transmitted by the ascensiontube is expressed by the number 1582*37. To this first effect we must add* that which weobtained from the return of the ram ; a suction tube which should arise from the space oc-cupied by the bed of air, plunged in a reservoir distant 0*975 metres from this bed, all thewater in this ascension tube would be furnished by the suction tube; therefore at eachminute the return of the ram would elevate 8*546 litres of water to a vertical height of0*975 metres. This effect is the measure of a force of 83*32, which being added to the firsteffect, 1582*37, gives for the total effect of the ram in one minute 1665 *65 ; but the force ex-pended in the same time is 22*12; the relation ^f a of these two numbers is still greater thanin the preceding examples.

Montgolfier projected at Marly a ram, which was at the same time a siphon and suction :the siphon form appeared to him most preferable, because it placed the greater part of thepipes of the body of the ram out of the water; the suction tube emptied the water filteredby a chest placed on the bed of the river, and there was no fear of a deposit of sand on thevalves or their orifices.

Fig. 1761. shows, 1st, a system, N 7 , of seven valves and seven orifices; 2d, a disc M',pierced with holes, through which the water enters the air reservoir L, fig. 1762.: ingeneral the number and size of the flowing orifices determine the relation of the velocityof the water in the body of the ram, and its issue through each orifice.