资料来源 : Webster's Revised Unabridged Dictionary (1913)

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.

   {Circular, 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, or Bifilar}, {micrometer}. See under {Bifilar}.

   {Micrometer} {caliper or 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.

   {Position micrometer}. See under {Position}.

   {Scale}, 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.

Position \Po*si"tion\, n. [F. position, L. positio, fr. ponere,
   positum, to put, place; prob. for posino, fr. an old
   preposition used only in comp. (akin to Gr. ?) + sinere to
   leave, let, permit, place. See {Site}, and cf. {Composite},
   {Compound}, v., {Depone}, {Deposit}, {Expound}, {Impostor},
   {Opposite}, {Propound}, {Pose}, v., {Posit}, {Post}, n.]
   1. The state of being posited, or placed; the manner in which
      anything is placed; attitude; condition; as, a firm, an
      inclined, or an upright position.

            We have different prospects of the same thing,
            according to our different positions to it. --Locke.

   2. The spot where a person or thing is placed or takes a
      place; site; place; station; situation; as, the position
      of man in creation; the fleet changed its position.

   3. Hence: The ground which any one takes in an argument or
      controversy; the point of view from which any one proceeds
      to a discussion; also, a principle laid down as the basis
      of reasoning; a proposition; a thesis; as, to define one's
      position; to appear in a false position.

            Let not the proof of any position depend on the
            positions that follow, but always on those which go
            before.                               --I. Watts.

   4. Relative place or standing; social or official rank; as, a
      person of position; hence, office; post; as, to lose one's
      position.

   5. (Arith.) A method of solving a problem by one or two
      suppositions; -- called also the {rule of trial and
      error}.

   {Angle of position} (Astron.), the angle which any line (as
      that joining two stars) makes with another fixed line,
      specifically with a circle of declination.

   {Double position} (Arith.), the method of solving problems by
      proceeding with each of two assumed numbers, according to
      the conditions of the problem, and by comparing the
      difference of the results with those of the numbers,
      deducing the correction to be applied to one of them to
      obtain the true result.

   {Guns of position} (Mil.), heavy fieldpieces, not designed
      for quick movements.

   {Position finder} (Mil.), a range finder. See under {Range}.
      

   {Position micrometer}, a micrometer applied to the tube of an
      astronomical telescope for measuring angles of position in
      the field of view.

   {Single position} (Arith.), the method of solving problems,
      in which the result obtained by operating with an assumed
      number is to the true result as the number assumed is to
      the number required.

   {Strategic position} (Mil.), a position taken up by an army
      or a large detachment of troops for the purpose of
      checking or observing an opposing force.

   Syn: Situation; station; place; condition; attitude; posture;
        proposition; assertion; thesis.