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▪ I. micrometer|maɪˈkrɒmɪtə(r)|
[ad. F. micromètre (Azout 1667), f. Gr. µῑκρό-ς small + µέτρον measure: see -meter.]
An instrument for measuring minute objects or differences of dimension.
1. An astronomical instrument applied to telescopes for the purpose of measuring very small angular distances.
Of this instrument, which was first invented by W. Gascoigne about 1640, there are several forms, as the annular micrometer or circular micrometer, dioptric micrometer (catadioptric micrometer) or double-image micrometer, double-refraction micrometer, duplex micrometer, filar micrometer, prism micrometer, ring micrometer, wire micrometer.
1670Flamsteed in Hone Every-day Bk. I. 1092, I..had Mr. Townly's Micrometer presented to me by Sir Jonas Moor. 1759Gentl. Mag. 72 The method of using Mr. Dollond's new catadioptric Micrometer. 1836Penny Cycl. V. 228/2 The double-refraction micrometer. 1853Herschel Pop. Lect. Sci. v. §17 (1873) 193 What astronomers call a ‘ring micrometer’. 1866Brande & Cox Dict. Sci., etc. II. 517/2 The prism micrometer..has this important defect [etc.]. 1883Encycl. Brit. XVI. 248/1 Grubb's duplex micrometer. Ibid. 249/2 Double-Image Micrometers with Divided Lenses... Ramsden's dioptric micrometer.
2. An instrument applied to the microscope for the purpose of measuring small objects.
c1790J. Imison Sch. Art I. 240 The new micrometer is nothing more than a stage (on which the objects are placed) moveable by a fine screw which has a hand..passing over the divisions of a graduated circle. 1855tr. Wedl's Rudim. Pathol. Histol. i. i. (Syd. Soc.) 10 The glass micrometer..has supplanted the..screw micrometer. 1866Brande & Cox Dict. Sci., etc. II. 518/1 The instruments in use among microscopists are Jackson's micrometer and the cobweb micrometer. 1877Darwin Forms of Fl. i. 16, I measured with the micrometer many specimens, both dry and wet.
3. An instrument used in machine-construction, watchmaking, etc., for obtaining an extreme degree of accuracy in measurement.
1884F. J. Britten Watch & Clockm. 76 The new one [a plug] may be gauged with a Micrometer or Registering Callipers.
4. attrib. and Comb., as micrometer cell, micrometer eye-piece, micrometer measurement, micrometer pointer, micrometer scale, micrometer slide, micrometer square, micrometer wheel, micrometer wire; micrometer balance, a balance for ascertaining minute weights with exactitude, esp. used for weighing coins; micrometer gauge, a gauge fitted with a micrometer, used in machine-making; micrometer-microscope, an apparatus for reading and subdividing the divisions of large astronomical and geodetical instruments; micrometer screw, a screw attached to optical and other instruments for the exact measurement of very small angles.
1875Knight Dict. Mech. 1431/2 Kenshaw's *micrometer-balance, invented about 1842, consists of a beam or steel⁓yard supported on a knife-edged fulcrum.
1898Allbutt's Syst. Med. V. 443 The lines which form the divisions of the *micrometer cell may be made more distinct [etc.].
1835Ure Philos. Manuf. 126 For very nice measurements Troughton's *micrometer eye-piece..may be attached to the instrument.
1902Marshall Metal Tools 10 Another very useful type of gauge for making fine measurements is the *micrometer gauge.
1835Ure Philos. Manuf. 96 *Micrometer measurements taken from the spectral image..are apt to lead to great fallacies.
1849R. V. Dixon Heat i. 25 The microscope e′ was hence called the *micrometer microscope.
1883Encycl. Brit. XVI. 249/2 A dull phosphorescence sufficient to make the *micrometer pointer..faintly visible.
1854Pereira's Pol. Light 45 A very minutely grooved surface..presents an iridescent appearance in white light... *Micrometer scales frequently present the same appearances.
1788Trans. Soc. Arts VI. 190 Moved by the *micrometer screw.
1883Encycl. Brit. XVI. 244/1 The oblong frame, containing the *micrometer slides.
1898Allbutt's Syst. Med. V. 441 The corpuscles..are reckoned by means of a series of *micrometer squares ruled over a certain area of the glass floor of the chamber or cell.
1862Catal. Internat. Exhib. II. xi. 23 The tangent back sight is elevated by a rack and pinion, the latter having a *micrometer wheel for finer readings.
1806J. A. Hamilton in Trans. Roy. Irish Acad. 111 In adjusting the telescope and *micrometer wires.
▪ II. micrometer
var. micrometre. |