250

Analogy belweem the Pump and Chinese Bellows . [Book III.

mto the other end : it consists of a narrow piece of hard wood of the samedepth as the groove, and of a length that rather exceeds the width ofthe groove. A hole is drilled through one end and a pin driven throuo-hit into the solid part of the cover, so that it turns Ireely on this pin, andcloses and opens a passage for the escape of the wind into the tuyere. Itis driven by the wind at every stroke of the piston against the oppositecheek of the groove, and thus prevents the wind from passing into theother end of the cylinder, as shown at Gr in No. 112. It is surprising howeasily this valve plays although its upper and lower edges rub against thesurfaces of the two covers—a trifling movement of the piston drives itagainst the cheek, and occasions a snapping sound somewhat like thatfrom the contact of metal.

When the inner cover was raised out of its place, the piston and indue-tion valves were exposed to view, and the simplicity and efficiency ofthese parts were in keeping with the rest: the two valves are mere flapsof paper, glued at their loioer edges to the under side of the openings,and hence they stand nearly perpendicular, instead of being suspended fromabove; the slightest impulse of‘ air closed them. The piston is half aninch thick, but is reduced at the edges to a quarter of one ; it appears tobe formed of two thin pieces which, United, are equal in thickness to thatmentioned; and between them are inserted two small sheets of moderatelystiff paper, which project an inch over every side. The part that pro-jects is folded at the Corners and turned over the edges of the piston;one sheet being turned one way, and the other the contrary, so that whenthe piston is moved, the air presses the paper against the sides of the bel-lows and renders the piston perfectly tight, on the same principle as thedouble cupped leathers of fire-engines and other forcing-pumps; and atthe same time without any perceptible increase of friction. The two pis-ton rods are half inch square, and work through ho-les in one end of thebox without any stuffing-box. The whole machine is of wood, exceptthe paper for the piston and valves. Although the instrument appears tobe a rectangular box, it is not exactly so, the bottom being a little widerthan the top.

It would be superfluous to point out the application of piston bellows toraise water, since they are perfect models of our atmospheric and forcing-pumps. Why, then, it may be asked are not the Chinese found in thepossession of the latter '! In reply to this question, it may be observed : 1.That from our imperfect knowledge of the people, it is not certain thatsuch machines have not been, and are not used to a limited extent in theinterior of that great empire. 2. That custom, and probably experience,have induced them, in common with other nations of the Oriental world,to give the preference to more simple devices—-to their chain pump, bam-boo wheel, &c., a preference which we know is in some instances basedon solid grounds: for example, the chain pump as used by them, raisesmore water with the same amount of labor, than any atmospheric or forc-ing-pump, if placed under the same circumstances. And as for the noriaor bamboo wheel, which driven by a current, raises water night a.nd day,and from 20 to 5Q feet, we are told thatit answers the purpose “as com-pletely as the most complicated European machine could do; and I willanswer for it [says Yan Braam] that it does not occasion an expense often dollars.” 3. A circumstance connected with one of their ancient as wellas modern scenic representations, shows that when th eforcing or spouüngof water is required, their artists are at noloss for devices to effect it; andthat, too, under very unusual circumstances. One of the pantomimes per-formed at Pekin is the “ Marriage of the Sea with the Land.” The