Micrometer \Mi*crom"e*ter\, n. [Micro- + -meter: cf. F.
microm[`e]tre.]
An instrument, used with a telescope or microscope, for
measuring minute distances, or the apparent diameters of
objects which subtend minute angles. The measurement given
directly is that of the image of the object formed at the
focus of the object glass.
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Circular micrometer, or Ring micrometer, a metallic ring
fixed in the focus of the object glass of a telescope, and
used to determine differences of right ascension and
declination between stars by observations of the times at
which the stars cross the inner or outer periphery of the
ring.
Double image micrometer, a micrometer in which two images
of an object are formed in the field, usually by the two
halves of a bisected lens which are movable along their
line of section by a screw, and distances are determined
by the number of screw revolutions necessary to bring the
points to be measured into optical coincidence. When the
two images are formed by a bisected object glass, it is
called a divided-object-glass micrometer, and when the
instrument is large and equatorially mounted, it is known
as a heliometer.
Double refraction micrometer, a species of double image
micrometer, in which the two images are formed by the
double refraction of rock crystal.
Filar micrometer, or Bifilar micrometer. See under
Bifilar.
Micrometer caliper or Micrometer gauge (Mech.), a caliper
or gauge with a micrometer screw, for measuring dimensions
with great accuracy.
Micrometer head, the head of a micrometer screw.
Micrometer microscope, a compound microscope combined with
a filar micrometer, used chiefly for reading and
subdividing the divisions of large astronomical and
geodetical instruments.
Micrometer screw, a screw with a graduated head used in
some forms of micrometers; turning the head one full
revolution advances the position of the tip of the screw
only by a little.
Position micrometer. See under Position.
Scale micrometer, or Linear micrometer, a minute and very
delicately graduated scale of equal parts used in the
field of a telescope or microscope, for measuring
distances by direct comparison.
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Ring \Ring\, n. [AS. hring, hrinc; akin to Fries. hring, D. & G.
ring, OHG. ring, hring, Icel. hringr, DAn. & SW. ring; cf.
Russ. krug'. Cf. Harangue, Rank a row,Rink.]
A circle, or a circular line, or anything in the form of a
circular line or hoop.
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2. Specifically, a circular ornament of gold or other
precious material worn on the finger, or attached to the
ear, the nose, or some other part of the person; as, a
wedding ring.
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Upon his thumb he had of gold a ring. --Chaucer.
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The dearest ring in Venice will I give you. --Shak.
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3. A circular area in which races are or run or other sports
are performed; an arena.
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Place me, O, place me in the dusty ring,
Where youthful charioteers contend for glory. --E.
Smith.
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4. An inclosed space in which pugilists fight; hence,
figuratively, prize fighting. "The road was an
institution, the ring was an institution." --Thackeray.
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5. A circular group of persons.
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And hears the Muses in a ring
Aye round about Jove's alter sing. --Milton.
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6. (Geom.)
(a) The plane figure included between the circumferences
of two concentric circles.
(b) The solid generated by the revolution of a circle, or
other figure, about an exterior straight line (as an
axis) lying in the same plane as the circle or other
figure.
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7. (Astron. & Navigation) An instrument, formerly used for
taking the sun's altitude, consisting of a brass ring
suspended by a swivel, with a hole at one side through
which a solar ray entering indicated the altitude on the
graduated inner surface opposite.
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8. (Bot.) An elastic band partly or wholly encircling the
spore cases of ferns. See Illust. of Sporangium.
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9. A clique; an exclusive combination of persons for a
selfish purpose, as to control the market, distribute
offices, obtain contracts, etc.
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The ruling ring at Constantinople. --E. A.
Freeman.
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Ring armor, armor composed of rings of metal. See Ring
mail, below, and Chain mail, under Chain.
Ring blackbird (Zool.), the ring ousel.
Ring canal (Zool.), the circular water tube which surrounds
the esophagus of echinoderms.
Ring dotterel, or Ringed dotterel. (Zool.) See
Dotterel, and Illust. of Pressiroster.
Ring dropper, a sharper who pretends to have found a ring
(dropped by himself), and tries to induce another to buy
it as valuable, it being worthless.
Ring fence. See under Fence.
Ring finger, the third finger of the left hand, or the next
the little finger, on which the ring is placed in
marriage.
Ring formula (Chem.), a graphic formula in the shape of a
closed ring, as in the case of benzene, pyridine, etc. See
Illust. under Benzene.
Ring mail, a kind of mail made of small steel rings sewed
upon a garment of leather or of cloth.
Ring micrometer. (Astron.) See Circular micrometer, under
Micrometer.
Saturn's rings. See Saturn.
Ring ousel. (Zool.) See Ousel.
Ring parrot (Zool.), any one of several species of Old
World parrakeets having a red ring around the neck,
especially Palaeornis torquatus, common in India, and
Palaeornis Alexandri of Java.
Ring plover. (Zool.)
(a) The ringed dotterel.
(b) Any one of several small American plovers having a
dark ring around the neck, as the semipalmated plover
(Aegialitis semipalmata).
Ring snake (Zool.), a small harmless American snake
(Diadophis punctatus) having a white ring around the
neck. The back is ash-colored, or sage green, the belly of
an orange red.
Ring stopper. (Naut.) See under Stopper.
Ring thrush (Zool.), the ring ousel.
The prize ring, the ring in which prize fighters contend;
prize fighters, collectively.
The ring.
(a) The body of sporting men who bet on horse races.
[Eng.]
(b) The prize ring.
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