上射式水轮

Overshot \O"ver*shot`\, a.
From {Overshoot}, v. t.

{Overshot wheel}, a vertical water wheel, the circumference
of which is covered with cavities or buckets, and which is
turned by water which shoots over the top of it, filling
the buckets on the farther side and acting chiefly by its
weight.


Wheel \Wheel\ (hw[=e]l), n. [OE. wheel, hweol, AS. hwe['o]l,
hweogul, hweowol; akin to D. wiel, Icel. hv[=e]l, Gr.
ky`klos, Skr. cakra; cf. Icel. hj[=o]l, Dan. hiul, Sw. hjul.
[root]218. Cf. {Cycle}, {Cyclopedia}.]
1. A circular frame turning about an axis; a rotating disk,
whether solid, or a frame composed of an outer rim, spokes
or radii, and a central hub or nave, in which is inserted
the axle, -- used for supporting and conveying vehicles,
in machinery, and for various purposes; as, the wheel of a
wagon, of a locomotive, of a mill, of a watch, etc.

The gasping charioteer beneath the wheel
Of his own car. --Dryden.

2. Any instrument having the form of, or chiefly consisting
of, a wheel. Specifically:
(a) A spinning wheel. See under {Spinning}.
(b) An instrument of torture formerly used.

His examination is like that which is made by
the rack and wheel. --Addison.

Note: This mode of torture is said to have been first
employed in Germany, in the fourteenth century. The
criminal was laid on a cart wheel with his legs and
arms extended, and his limbs in that posture were
fractured with an iron bar. In France, where its use
was restricted to the most atrocious crimes, the
criminal was first laid on a frame of wood in the form
of a St. Andrew's cross, with grooves cut transversely
in it above and below the knees and elbows, and the
executioner struck eight blows with an iron bar, so as
to break the limbs in those places, sometimes finishing
by two or three blows on the chest or stomach, which
usually put an end to the life of the criminal, and
were hence called coups-de-grace -- blows of mercy. The
criminal was then unbound, and laid on a small wheel,
with his face upward, and his arms and legs doubled
under him, there to expire, if he had survived the
previous treatment. --Brande.
(c) (Naut.) A circular frame having handles on the
periphery, and an axle which is so connected with the
tiller as to form a means of controlling the rudder
for the purpose of steering.
(d) (Pottery) A potter's wheel. See under {Potter}.

Then I went down to the potter's house, and,
behold, he wrought a work on the wheels. --Jer.
xviii. 3.

Turn, turn, my wheel! This earthen jar
A touch can make, a touch can mar. --Longfellow.
(e) (Pyrotechny) A firework which, while burning, is
caused to revolve on an axis by the reaction of the
escaping gases.
(f) (Poetry) The burden or refrain of a song.

Note: ``This meaning has a low degree of authority, but is
supposed from the context in the few cases where the
word is found.'' --Nares.

You must sing a-down a-down,
An you call him a-down-a.
O, how the wheel becomes it! --Shak.

3. A bicycle or a tricycle; a velocipede.

4. A rolling or revolving body; anything of a circular form;
a disk; an orb. --Milton.

5. A turn revolution; rotation; compass.

According to the common vicissitude and wheel of
things, the proud and the insolent, after long
trampling upon others, come at length to be trampled
upon themselves. --South.

[He] throws his steep flight in many an a["e]ry
wheel. --Milton.

{A wheel within a wheel}, or {Wheels within wheels}, a
complication of circumstances, motives, etc.

{Balance wheel}. See in the Vocab.

{Bevel wheel}, {Brake wheel}, {Cam wheel}, {Fifth wheel},
{Overshot wheel}, {Spinning wheel}, etc. See under {Bevel},
{Brake}, etc.

{Core wheel}. (Mach.)
(a) A mortise gear.
(b) A wheel having a rim perforated to receive wooden
cogs; the skeleton of a mortise gear.

{Measuring wheel}, an odometer, or perambulator.

{Wheel and axle} (Mech.), one of the elementary machines or
mechanical powers, consisting of a wheel fixed to an axle,
and used for raising great weights, by applying the power
to the circumference of the wheel, and attaching the
weight, by a rope or chain, to that of the axle. Called
also {axis in peritrochio}, and {perpetual lever}, -- the
principle of equilibrium involved being the same as in the
lever, while its action is continuous. See {Mechanical
powers}, under {Mechanical}.

{Wheel animal}, or {Wheel animalcule} (Zo["o]l.), any one of
numerous species of rotifers having a ciliated disk at the
anterior end.

{Wheel barometer}. (Physics) See under {Barometer}.

{Wheel boat}, a boat with wheels, to be used either on water
or upon inclined planes or railways.

{Wheel bug} (Zo["o]l.), a large North American hemipterous
insect ({Prionidus cristatus}) which sucks the blood of
other insects. So named from the curious shape of the
prothorax.

{Wheel carriage}, a carriage moving on wheels.

{Wheel chains}, or {Wheel ropes} (Naut.), the chains or ropes
connecting the wheel and rudder.

{Wheel cutter}, a machine for shaping the cogs of gear
wheels; a gear cutter.

{Wheel horse}, one of the horses nearest to the wheels, as
opposed to a leader, or forward horse; -- called also
{wheeler}.

{Wheel lathe}, a lathe for turning railway-car wheels.

{Wheel lock}.
(a) A letter lock. See under {Letter}.
(b) A kind of gunlock in which sparks were struck from a
flint, or piece of iron pyrites, by a revolving wheel.
(c) A kind of brake a carriage.

{Wheel ore} (Min.), a variety of bournonite so named from the
shape of its twin crystals. See {Bournonite}.

{Wheel pit} (Steam Engine), a pit in the ground, in which the
lower part of the fly wheel runs.

{Wheel plow}, or {Wheel plough}, a plow having one or two
wheels attached, to render it more steady, and to regulate
the depth of the furrow.

{Wheel press}, a press by which railway-car wheels are forced
on, or off, their axles.

{Wheel race}, the place in which a water wheel is set.

{Wheel rope} (Naut.), a tiller rope. See under {Tiller}.

{Wheel stitch} (Needlework), a stitch resembling a spider's
web, worked into the material, and not over an open space.
--Caulfeild & S. (Dict. of Needlework).

{Wheel tree} (Bot.), a tree ({Aspidosperma excelsum}) of
Guiana, which has a trunk so curiously fluted that a
transverse section resembles the hub and spokes of a
coarsely made wheel. See {Paddlewood}.

{Wheel urchin} (Zo["o]l.), any sea urchin of the genus
{Rotula} having a round, flat shell.

{Wheel window} (Arch.), a circular window having radiating
mullions arranged like the spokes of a wheel. Cf. {Rose
window}, under {Rose}.

Water wheel \Wa"ter wheel`\
1. Any wheel for propelling machinery or for other purposes,
that is made to rotate by the direct action of water; --
called an {overshot wheel} when the water is applied at
the top, an {undershot wheel} when at the bottom, a
{breast wheel} when at an intermediate point; other forms
are called {reaction wheel}, {vortex wheel}, {turbine
wheel}, etc.

2. The paddle wheel of a steam vessel.

3. A wheel for raising water; a noria, or the like.