277
Chap. 4.]
of bees closely examined, it would doubtless be found that the relativediameters of their proboscis and of the cells, and the area of the (bellows)pumps in their bodies, are such as are best adaptedto the muscular energy which they employ in work-ing the latter. Were it otherwise, a greater forcemight be requiredto inject the honey and drive for-ward the piston, than they possess. In the case ofa hydrostatic press, when the resistance is too greatto be overeome by an injection pump of large dia-meter, one of smaller bore is employed.
We shall now produce a few specimens of forc-ing pumps with hollow pistons, or such as admit wa-ter to pass through them. If a common atmosphericpump be inverted, its cylinder immersed in water,and the valves of the upper and lower boxes re versedas in the figure, it becomes a forcing, or, as it issometimes named, a lifting pump; because the Con-tents of the cylinder are lifted up when the piston israised, instead of being driven out from below by itsdescent, as in Nos. 116, 117, In a lifting pump theliquid is expelled from the top of the cylinder—ina forcing one from the bottom—it is the waterabove the piston that is raised by the former; and that which enters be-low it, by the latter. The piston rod in the figure is attached to an ironframe that is suspended to thb end of a beam or lever as in Nos. 123, 124.The valve on the top of the piston, like that at the end of the cylinder,opens upwards. When the piston descends (whichit does by its own weight and that of the frame) itsvalve opens and the water enters the upper part ofthe cylinder, then as soon as it begins to rise itsvalve closes, and the liquid above it is forced up theascending pipe. Upon the return of the piston theupper valve is shut by the weight of the columnabove it, the cylinder is again charged and its Con-tents forced up by a repetition of the movements.Machines of this description are of old date. Theywere formerly employed in raising water frommines. They were adopted by Rannequin in thecelebrated water-works at Marli; and by Lintlaerin the engines he erected during the reign of Henry4th, at Pont Neuf , to supply the Louvre from theriver Seine. -
As they cannot in all locations be inserted con«veniently in the reservoir containing the water tobe raised, they have sometimes been placed in cis-terns erected above the original source, and sup-plied by atmospheric pumps extending to it, as inNo. 127. The cylinder of the atmospheric pumpterminates in the bottom of the cistern, and is plac-ed directly under that of the lifting one; the pistonsof both being attached to the same rod and workedby the same frame. Such was the construction ofthe old Parisian water-works at the bridge of No-tre Dame. These consisted of a series of pumpsarranged as in the figure. and worked by an undershot wheel.