Tread Wheel .

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Chap. lO.j

the bücket, so that when the bücket is in the well, the same rope is allwound on tbe greater wheel, [drum] the end whereof may be taken onthe shoulder, and the man may walk or run forwards, tili the bücket bedrawn up. The bücket may have a round hole in the midst of the bot-tom with a cover fitted to it, like the sucker of a pump, that when thebücket rests on the water, the hole may open and the bücket fill.” Dic-tionarium Rusticum, Lon. 1704. See No. 23.

This is one of the modes of raising heavy weights, described by Vitru-vius, in Book X of his Architecture, and is so figured in some of the oldeditions, that of Barbaro for example. Venice 1567. It appears to have beenadopted to raise water from the deep Wells of Asia in anoient times, andis still continued in use there. In Sym’s Embassy to Ava, there is a noticeof the Petroleum Wells, the oil from which is universally employedthroughout the Birman empire. One which he examined was four feetsquare, and thirty-seven fathoms, [222 feet] deep. The water and oil“ were drawn up in an iron pot, fastened to a rope passed over a woodencylinder, which revolves on an axis supported by two upright posts.When the pot is filled, two men take the rope by the end, and run downa declivity, which is cut in the ground to a distance equivalent to the depthof the well; thus when they reach the end of their track, the pot israised to its proper elevation.” 3 The contents, water and oil, are then dis-charged into a cistern, and the water is afterwards drawn off through ahole in the bottom. A ratchet wheel and click to detain the bücket whenelevated, would enable a single person to work this machine, or thebücket might be suspended to its bail by swivels, and overturned at thetop by a catch, as in No. 16.

No, 24. Tread Wheel .

Another mode of communicating motion to the roller, is by means of atread wheel, attached like the drum in figure 23, to one end of it. Inthis, a man or an animal walks or rather climbs up one side, somewhatike a squirrel m its cage, and by his weight turns the wheel, and raisesthe water, as represented in No. 24.

This appears to have been a common mode of applying human effortamong the ancients. Some of their cranes for raising columns and other

1° A Y a >. L° n ' 1800, vol. iii, 236. See also an account of these wells, andmoaes of raismg their contents, in vol. ix, of Tilloch ’s Phil. Mag. p. 226.

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