230

Cex , 'rjfugal Pumps.

[Book II.

Charge the water into a circular trough, over which they turn. To chargeit, the orifices may be closed by loosely inserting a cork into each, andthen filling the pump through an opening at the top which is then closedby a screw cap. A rapid rotary motion is imparted to the machine by apulley fixed on the axis and driven by a band, from a drum, &c. Thecentrifugal force thus communicated to the water in thearms or transverse tube, throws it out; and the atmo-sphere pushes up the perpendicular one fresh portionsto supply the place of those ejected. These pumps aresometimes made with a single arm like the letter L in-verted; at others quite a number radiate from the up-right one. It has also been made of a series of tubesarranged round a vertical shaft in the form of an inver-ted cone. A valuable improvement was submitted byM. Jorge to the French Academy in 1816. It consistsin imparting motion to the arms only, thus saving thepower consumed in moving the upright tube, and bywhich the latter can be inclined as circumstances or lo-cations may require.

A combination of the centrifugal pump with Parenfsor Barker’s mill, was proposed by Dr. West, which insome locations may be adopted with advantage. It is sim-ply a vertical shaft round which two tubes are wound:(No. 96) the upper one is the pump; the lower one the^mill. The area of the lower one should be to that of theupper in the inverse ratio of the perpendicular height,and as much more as is necessary to overcome the fric-tion. The cup or basin into which the stream (part ofwhich is to be raised) is directed, may be attached to the shaft and turnwith it, or the latter may pass through it. Tilloch ’s Phil. Mag. vol. xi.

The first centrifugal pump appears to havebeen invented by M. Le Demour, whosent a description of it to the FrenchAcademy in 1732. (Machines approuve.Tom. vi, p. 9.) It was merely a straighttube attached in an inclined position to avertical axis, and whirled round hy thehandle—the tube was fastened by liga-tures to three Strips of wood projectingfrom the axis, as shown at No. 97.

With this pump we close our remarkson devices for raising water by atmo-spheric pressure; more might have beenadded, but as nearly all the machines yetto be described illustrate the same prin-ciple, the reader is referred to the fol-lowing Books, and particularly to the at-mospheric and forcing pumps described inthe next one.

[The vessels under the pump spouts in Nos. 90, 93 and 94, are Romanbronze buckets from Pompeii.]

No. 96. West’sPump.

No. 97. Le Demour’s Pump,

END OF THE SECOND BOOK.