micrometer microscope

An instrument used for reading and subdividing the divisions of large astronomical and geodetical instruments. micrometer-screw, subst . A screw attached to optical and mathematical instruments as a means for exact measurement of very small angles. The great space through which the lever of the screw pa es, in comparison with the longitudinal motion due to the pitch, affords the means for a positive motion which is imperceptible on the object moved, though appreciable in its results. If the thread of a micrometer-screw in an instrument has 50 threads to an inch, and carries a pointer which traverses a graduated circle divided into 20 equal parts, the revolution of the micrometer-screw for a distance equal to one of the divisions will move the object to which the screw is attached Tods of an inch; that is, 20 x 50=1,000. mi-cro-mět-ric, mi-cro-met-ric-al, a . [Eng. micrometer; -ic, -ical .] Of or pertaining to the micrometer; as, micrometric measurements. mi-cro-met-ric-al-ly, adv. [Eng. micrometric al; -ly.] By means of a micrometer.