206

Bellows Pump.

[Book II,

a bag, resembling the old powder-puff or the modern accordion; others intbe form of the domestic and blacksmith’s bellows—some in the fignreof a drum, and others as a portion of one—as a simple horizontal tubesuspended at the centre on a perpendicular one, and whirled round likethe arms of a potter’s wheel—then again as a perpendicular tube withoutsucker or piston, and moved like a gentleman’s walking cane, from whichindeed its name is derived. (See Garne Hydraulique in Book IV.) Theyhave also been made of two simple tubes, one moved over the other likethose of a telescope—even a kettle or cauldron has been used as a pump,and the vapor of its boiling water substituted for the sucker to expel theair it contained, after which the pressure of the at-mosphere forced water into it from below. In fine,any device by which air can be removed from theinterior of a vessel, is, or may be used as a pump toraise water.

Nor have the ‘suckers’ or‘pistons’ been subjectto less changes than other parts of pumps. Theyhave been made solid and hollow—in the form ofcones, cylinders, pyramids, sectors, and Segments ofcircles:—in the shape of cog-wheels, and of thearms and vanes of wind-mills, with motions analogousto such as these; and sometimes they are made inthe shape of a gentleman’s hat and of similar mate-rials; while the only motion imparted to them, isthe odd one of alternately pushin g them inside outand outside in.

If a collapsed bladder or leather bag, be securedat its orifice to the upper end of a perpendiculartube whose lower end is placed in a vessel of water,(No. 80) then, if by some contrivance the bag can be distended, as shownby the dotted lines, the small quantity of air contained in it and the pipewould become rarefied, and consequently unableto balance the pressure without—hence the liquidwould be forced up into the bag, until the air withinbecame again Condensed as before—that is, the blad-der would be filled with water, with the exceptionof a quantity equal to the space previously occupiedby the air within it and the pipe.

To convert this simple apparatus into a pump, twovalves or clacks only are wanting. One, openingup-wards and placed in any part of the pipe or at eitherof its extremities. This will allow water to passupthrough it, but none to descend. The other placedover an aperture made on the top of the bag, andopening outwards—through this the contents of thevessel when collapsed can be discharged; and whendistended it will close, and thereby prevent the en-trance of the external air. The instrument thus ar-anged becomes a bellows pump, (No. 81,) a machine,which from the obvious application of the bellows toraise and spout water as well as air, has been re-invented by machinists in almost every age.

The figure scarcely requires Illustration. It repre-sents a pipe attached to the under board of a circularor lantern bellows, the orifice of which is covered by a clack—the upper

No. 80.

No. 81. Bellows Pump.