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Positive eyepiece
(gcide) | Positive \Pos"i*tive\, a. [OE. positif, F. positif, L.
positivus. See Position.]
1. Having a real position, existence, or energy; existing in
fact; real; actual; -- opposed to negative. "Positive
good." --Bacon.
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2. Derived from an object by itself; not dependent on
changing circumstances or relations; absolute; -- opposed
to relative; as, the idea of beauty is not positive, but
depends on the different tastes individuals.
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3. Definitely laid down; explicitly stated; clearly
expressed; -- opposed to implied; as, a positive
declaration or promise.
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Positive words, that he would not bear arms against
King Edward's son. --Bacon.
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4. Hence: Not admitting of any doubt, condition,
qualification, or discretion; not dependent on
circumstances or probabilities; not speculative;
compelling assent or obedience; peremptory; indisputable;
decisive; as, positive instructions; positive truth;
positive proof. "'T is positive 'gainst all exceptions."
--Shak.
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5. Prescribed by express enactment or institution; settled by
arbitrary appointment; said of laws.
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In laws, that which is natural bindeth universally;
that which is positive, not so. --Hooker.
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6. Fully assured; confident; certain; sometimes,
overconfident; dogmatic; overbearing; -- said of persons.
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Some positive, persisting fops we know,
That, if once wrong, will needs be always. --Pope.
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7. Having the power of direct action or influence; as, a
positive voice in legislation. --Swift.
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8. (Photog.) Corresponding with the original in respect to
the position of lights and shades, instead of having the
lights and shades reversed; as, a positive picture.
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9. (Chem.)
(a) Electro-positive.
(b) Hence, basic; metallic; not acid; -- opposed to
negative, and said of metals, bases, and basic
radicals.
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10. (Mach. & Mech.)
(a) Designating, or pertaining to, a motion or device in
which the movement derived from a driver, or the grip
or hold of a restraining piece, is communicated
through an unyielding intermediate piece or pieces;
as, a claw clutch is a positive clutch, while a
friction clutch is not.
(b) Designating, or pertaining to, a device giving a
to-and-fro motion; as, a positive dobby.
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11. (Vehicles) Designating a method of steering or turning in
which the steering wheels move so that they describe
concentric arcs in making a turn, to insure freedom from
side slip or harmful resistance.
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Positive crystals (Opt.), a doubly refracting crystal in
which the index of refraction for the extraordinary ray is
greater than for the ordinary ray, and the former is
refracted nearer to the axis than the latter, as quartz
and ice; -- opposed to negative crystal, or one in which
this characteristic is reversed, as Iceland spar,
tourmaline, etc.
Positive degree (Gram.), that state of an adjective or
adverb which denotes simple quality, without comparison or
relation to increase or diminution; as, wise, noble.
Positive electricity (Elec), the kind of electricity which
is developed when glass is rubbed with silk, or which
appears at that pole of a voltaic battery attached to the
plate that is not attacked by the exciting liquid; --
formerly called vitreous electricity; -- opposed to
negative electricity.
Positive eyepiece. See under Eyepiece.
Positive law. See Municipal law, under Law.
Positive motion (Mach.), motion which is derived from a
driver through unyielding intermediate pieces, or by
direct contact, and not through elastic connections, nor
by means of friction, gravity, etc.; definite motion.
Positive philosophy. See Positivism.
Positive pole.
(a) (Elec.) The pole of a battery or pile which yields
positive or vitreous electricity; -- opposed to
negative pole.
(b) (Magnetism) The north pole. [R.]
Positive quantity (Alg.), an affirmative quantity, or one
affected by the sign plus [+].
Positive rotation (Mech.), left-handed rotation.
Positive sign (Math.), the sign [+] denoting plus, or more,
or addition.
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Positive eyepiece
(gcide) | eyepiece \eye"piece`\ eye-piece \eye"-piece`\, n. (Opt.)
The lens, or combination of lenses, at the eye end of a
microscope, telescope or other optical instrument, through
which the image formed by the mirror or object glass is
viewed.
Syn: ocular.
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Collimating eyepiece. See under Collimate.
Negative, or Huyghenian, eyepiece, an eyepiece
consisting of two plano-convex lenses with their curved
surfaces turned toward the object glass, and separated
from each other by about half the sum of their focal
distances, the image viewed by the eye being formed
between the two lenses. it was devised by Huyghens, who
applied it to the telescope. Campani applied it to the
microscope, whence it is sometimes called {Campani's
eyepiece}.
Positive eyepiece, an eyepiece consisting of two
plano-convex lenses placed with their curved surfaces
toward each other, and separated by a distance somewhat
less than the focal distance of the one nearest eye, the
image of the object viewed being beyond both lenses; --
called also, from the name of the inventor, {Ramsden's
eyepiece}.
terrestrial, or Erecting eyepiece, an eyepiece used in
telescopes for viewing terrestrial objects, consisting of
three, or usually four, lenses, so arranged as to present
the image of the object viewed in an erect position.
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