372
Canne Hydrawlique
of these machines. Without them, the pipes would soon be ruptured by theviolent concussion consequent on the sudden stoppage of the efflux of themotive column. They perform a similar part to that of the bags of wool, &c.which the ancients, when besieged, interposed between their walls and thebattering rams of the besiegers, in Order to bröak the force of the blows.
The ram has also been used in a few cases to raise water by atmos-pheric pressure from a lower level, so as to discharge it at the same levelwith the motive column or even higher. See Siphon Ram, in next book.
The device by which Montgolfier made the ram self-acting, is one ofthe neatest imaginable. It is unique : there never was any thing like itin practical hydraulics, or in the whole ränge of the arts ; and its simpli-city is equal to its novelty, and useful effects. Perhaps it may be said thathe only added a valve to Whitehurst’s machine : be it so—but that sim-ple valve instantly changed, as by magic, the whole character of the ap -paratus—like the mere change of the cap, which transformed the LeechHakim into Saladin. ® And the emotions of Coeur de Lion, upon Undinghis great adversary had been his physician in disguise, were not more ex-quisite than those, which an admirer of this department of philosophy ex-periences, when he contemplates for the first time the metamorphosis ofthe English machine by the French Savan. The name of Montgolfierwill justly be associated with this admirable machine in future ages.When all political and ecclesiastical crusaders are forgotten, and the me-mories of all who have hewed a passage to notoriety merely by the sword,will be detested—the name of its inventor will be embalmea in the recol-lections of an admiring posterity.
The water cane, or canne hydrauliqne, raises water in a different man-ner from any apparatus yet described. A modifieation of it in miniaturehas long been employed in the lecture room, but it is seldom met with indescriptions of hydraulic machines. It is represented at No. 170 ; and
consists of a vertical tube, in out-ward appearance like a walkingcane, having a valve opening up-wards at the bottom, and placedin the liquid to be raised. Sup-pose the lower end twelve or fif-teen inches below the surface, thewater of course would enterthrough the valve and stand atthe same height within as with-out : now if the tube were raisedquickly, but not entirely out ofthe water, the valve would closeand the liquid within would becarried up with it; and if, whenthe tube was at the highest pointof the stroke, its motion was sttd-denly reversed (by jerking it back)the liquid column within wouldstill continue to ascend until themomentum imparted to it at thefirst was expended ; hence a va-cuity would be left in the lowerpart of the instrument into which, fresh portion of water would enter, and by repeating the Operation the
" Walter Scotfs Tales of th6 Crusaders.
No. 170
No. 17t
No. 172.