Mi·crom·e·ter n.  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 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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 Po·si·tion 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.