equatorialadj.n.
/ɛkwəˈtɔːrɪəl//iːkwəˈtɔːrɪəl/ A. adj.
1.
a. Of or pertaining to the equator; situated or existing on or about the equator.
ΘΚΠ
the world > the earth > geodetic references > [adjective] > latitude > equator
equinoctial1595
equatorial1713
1713 W. Derham Physico-theol. ii. i. 39 A prolate Sphæroid, making the Polar about 34 Miles shorter than the Equatorial Diameter.
1789 Herschel in Philos. Trans. (Royal Soc.) 80 16 The arrangement of the belts..has always followed the direction of the ring, which is what I have called being equatorial.
1799 W. Jones Adams's Lect. Nat. & Exper. Philos. (ed. 2) III. xxxii. App. 379 Their surfaces will be higher..in the equatoreal than in the polar regions.
1860 M. F. Maury Physical Geogr. Sea (ed. 8) v. §296 Panama is in the region of equatorial calms.
1870 J. Yeats Nat. Hist. Commerce 65 Equatorial grains are maize and rice.
b. Pertaining to the ‘equator’ of a magnet, or of any spherical or spheroidal body.
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the world > matter > physics > electromagnetic radiation > magnetism > magnetic devices or materials > [adjective] > polar > relating to equator
equatorial1664
1664 H. Power Exper. Philos. iii. 168 Those aequatorial parts of the Magnet, which before respected the East.
1837 D. Brewster Treat. Magnetism 268 The middle of a copper wire..was applied to the equatorial groove.
1861 J. R. Greene Man. Animal Kingdom II. 227 In Cestum..these [a pair of symmetrical tentacles] do not..issue from the equatorial region, thence turning away from the mouth.
c. Pertaining to the equator of a balloon (cf. equator n. 3d).
ΘΚΠ
society > travel > air or space travel > a means of conveyance through the air > balloons and airships > [adjective] > line of maximum horizontal section
equatorial1838
1838 M. Mason Aeronautica 30 In shape it [sc. a balloon] somewhat resembles a pear; its upright or polar diameter exceeding the transverse or equatorial by about one-sixth.
2. equatorial instrument (also equatorial telescope): an apparatus consisting essentially of a telescope attached by an arm to an axle revolving in a direction parallel to the plane of the equator. By a uniform motion given to this axle (in large instruments by clockwork) the telescope follows the diurnal apparent motion of any point in the heavens to which it is directed. equatorial circle: a graduated circle (otherwise called hour-circle, right-ascension-circle) revolving in a plane parallel to the equator, forming part of the equatorial instrument.
ΘΚΠ
the world > physical sensation > sight and vision > optical instruments > instrument for distant vision > [noun] > telescope > equatorial telescope
equatorial instrument1791
equatorial1793
1791 T. Jefferson in Harper's Mag. (1885) Mar. 535/2 He is to pay for equatorial instrument.
1793 G. Shuckburgh Equator. Instr. in Philos. Trans. (Royal Soc.) 83 72 The idea of an equatorial telescope was again renewed by three several artists in this kingdom.
1868 G. B. Airy Pop. Astron. (ed. 6) ii. 39 For causing the Equatoreal instrument to revolve uniformly.
3. Biology. equatorial plate [translating French plaque équatoriale (E. van Beneden 1875, in Bull. de l'Acad. R. d. Sci. de Belg. (Classe des Sciences) 2me Sér. XL. 733)] : (in mitosis and meiosis) the position occupied by the chromosomes when arranged in the equatorial plane of the spindle during metaphase. Cf. equator n. 3e.
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1887 A. C. Haddon Introd. Study Embryol. ii. 19 At the stage when the chromatin is equatorially situated (the ‘equatorial plate’, which is the equivalent of the wreath and aster stage), the achromatin forms a well-marked spindle-shaped bundle of fibres.
1896 E. B. Wilson Cell ii. 49 The chromosomes group themselves in a plane passing through the equator of the spindle, and thus form what is known as the equatorial plate.
1913 J. W. Jenkinson Vertebr. Embryol. iii. 40 The plane at right angles to the axis and including the centre of the egg is equatorial.
1952 A. F. W. Hughes Mitotic Cycle iv. 116 During metaphase the chromosomes move from random positions into the ‘equatorial plate’.
1958 C. P. Swanson Cytol. & Cytogenetics iii. 52 The spindle..serves to bring the chromosomes onto the metaphase, or equatorial, plate.
1960 L. Picken Organization of Cells x. 501 Either before fertilization or at the eight-cell stage, an equatorial separation of the two halves of the egg gives rise to qualitatively different larvae.
4. equatorial migration n. migration of fish along the lines of longitude, i.e. northwards or southwards.
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1879 G. B. Goode Hist. Menhaden in Rep. Commissioner 1877 (U.S. Comm. Fish & Fisheries) V. App. A. 51 The former may be called equatorial, the latter [i.e. changing to waters of less or greater depth] bathic migration.
B. n.
= equatorial instrument at sense A. 2.
ΘΚΠ
the world > physical sensation > sight and vision > optical instruments > instrument for distant vision > [noun] > telescope > equatorial telescope
equatorial instrument1791
equatorial1793
1793 Philos. Trans. (Royal Soc.) 83 84 The equatorial is a machine calculated to observe the heavenly bodies in every part of the hemisphere.
1847 W. Whewell Hist. Inductive Sci. (rev. ed.) II. vii. vi. §1 Transit instruments, equatorials, heliometers.
1879 J. N. Lockyer Elem. Lessons Astron. (new ed.) vi. 224 An equatorial.
Compounds
equatorial clock a clock for driving an equatorial (see sense B.).
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1884 F. J. Britten Watch & Clockmakers' Handbk. (new ed.) 66 Conical pendulums are not much used except for equatorial clocks.
1884 F. J. Britten Watch & Clockmakers' Handbk. (new ed.) 102 Equatorial Clock, a clock for driving an equatorial telescope. It has generally a conical pendulum or other device for rendering its motion continuous.
This entry has not yet been fully updated (first published 1891; most recently modified version published online December 2021).
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adj.n.1664