Part 3883

<p><b>2.</b> <fld>(Math.)</fld> <def>An expression of the condition of equality between two algebraic quantities or sets of quantities, the sign = being placed between them; <as>as, a binomial <ex>equation</ex>; a quadratic <ex>equation</ex>; an algebraic <ex>equation</ex>; a transcendental <ex>equation</ex>; an exponential <ex>equation</ex>; a logarithmic <ex>equation</ex>; a differential <ex>equation</ex>, etc.</as></def>

<p><b>3.</b> <fld>(Astron.)</fld> <def>A quantity to be applied in computing the mean place or other element of a celestial body; that is, any one of the several quantities to be added to, or taken from, its position as calculated on the hypothesis of a mean uniform motion, in order to find its true position as resulting from its actual and unequal motion.</def>

<cs><col>Absolute equation</col>. <cd>See under <er>Absolute</er>.</cd> -- <mcol><col>Equation box</col>, &or; <col>Equational box</col></mcol>, <cd>a system of differential gearing used in spinning machines for regulating the twist of the yarn. It resembles gearing used in equation clocks for showing apparent time.</cd> -- <col>Equation of the center</col> <fld>(Astron.)</fld>, <cd>the difference between the place of a planet as supposed to move uniformly in a circle, and its place as moving in an ellipse.</cd> -- <col>Equations of condition</col> <fld>(Math.)</fld>, <cd>equations formed for deducing the true values of certain quantities from others on which they depend, when different sets of the latter, as given by observation, would yield different values of the quantities sought, and the number of equations that may be found is greater than the number of unknown quantities.</cd> -- <col>Equation of a curve</col> <fld>(Math.)</fld>, <cd>an equation which expresses the relation between the co\'94rdinates of every point in the curve.</cd> -- <col>Equation of equinoxes</col> <fld>(Astron.)</fld>, <cd>the difference between the mean and apparent places of the equinox.</cd> -- <col>Equation of payments</col> <fld>(Arith.)</fld>, <cd>the process of finding the mean time of payment of several sums due at different times.</cd> -- <col>Equation of time</col> <fld>(Astron.)</fld>, <cd>the difference between mean and apparent time, or between the time of day indicated by the sun, and that by a perfect clock going uniformly all the year round.</cd> -- <mcol><col>Equation</col> <col>clock &or; watch</col></mcol>, <cd>a timepiece made to exhibit the differences between mean solar and apparent solar time. <i>Knight</i>.</cd> -- <col>Normal equation</col>. <cd>See under <er>Normal</er>.</cd> -- <col>Personal equation</col> <fld>(Astron.)</fld>, <cd>the difference between an observed result and the true qualities or peculiarities in the observer; particularly the difference, in an average of a large number of observation, between the instant when an observer notes a phenomenon, as the transit of a star, and the assumed instant of its actual occurrence; or, relatively, the difference between these instants as noted by two observers. It is usually only a fraction of a second; -- sometimes applied loosely to differences of judgment or method occasioned by temperamental qualities of individuals.</cd> -- <col>Theory of equations</col> <fld>(Math.)</fld>, <cd>the branch of algebra that treats of the properties of a single algebraic equation of any degree containing one unknown quantity.</cd></cs>

<h1>Equator</h1> <Xpage=504>

<hw>E*qua"tor</hw> <tt>(?)</tt>, <tt>n.</tt> <ety>[L. <ets>aequator</ets> one who equalizes: cf. F. <ets>\'82quateur</ets> equator. See <er>Equate</er>.]</ety>

<p><b>1.</b> <fld>(Geog.)</fld> <def>The imaginary great circle on the earth's surface, everywhere equally distant from the two poles, and dividing the earth's surface into two hemispheres.</def>

<p><b>2.</b> <fld>(Astron.)</fld> <def>The great circle of the celestial sphere, coincident with the plane of the earth's equator; -- so called because when the sun is in it, the days and nights are of equal length; hence called also the <altname>equinoctial</altname>, and on maps, globes, etc., the <altname>equinoctial line</altname>.</def>

<cs><mcol><col>Equator</col> <col>of the sun &or; of a planet</col></mcol> <fld>(Astron.)</fld>, <cd>the great circle whose plane passes through through the center of the body, and is perpendicular to its axis of revolution.</cd> -- <col>Magnetic equator</col>. <cd>See <er>Aclinic</er>.</cd></cs>

<h1>Equatorial</h1> <Xpage=504>

<hw>E`qua*to"ri*al</hw> <tt>(?)</tt>, <tt>a.</tt> <ety>[Cf. F. <ets>\'82quatorial</ets>.]</ety> <def>Of or pertaining to the equator; <as>as, <ex>equatorial</ex> climates</as>; also, pertaining to an equatorial instrument.</def>

<h1>Equatorial</h1> <Xpage=504>

<hw>E`qua*to"ri*al</hw>, <tt>n.</tt> <fld>(Astron.)</fld> <def>An instrument consisting of a telescope so mounted as to have two axes of motion at right angles to each other, one of them parallel to the axis of the earth, and each carrying a graduated circle, the one for measuring declination, and the other right ascension, or the hour angle, so that the telescope may be directed, even in the daytime, to any star or other object whose right ascension and declination are known. The motion in right ascension is sometimes communicated by clockwork, so as to keep the object constantly in the field of the telescope. Called also an <altname>equatorial telescope</altname>.</def>

<note>&hand; The term <i>equatorial</i>, or <i>equatorial instrument</i>, is sometimes applied to any astronomical instrument which has its principal axis of rotation parallel to the axis of the earth.</note> <-- contrasted with altazimuthal movement of a telescope. -->

<h1>Equatorially</h1> <Xpage=504>

<hw>E`qua*to"ri*al*ly</hw>, <tt>adv.</tt> <def>So as to have motion or direction parallel to the equator.</def>

<h1>Equerry</h1> <Xpage=504>

<hw>Eq"uer*ry</hw> <tt>(?; 277)</tt>, <tt>n.</tt>; <plu>pl. <plw>Equerries</plw> <tt>(#)</tt></plu>. <ety>[F. <ets>\'82curie</ets> stable, for older <ets>escurie</ets>, <ets>escuirie</ets> (confused somewhat with F. <ets>\'82cuyer</ets>, OF. <ets>escuyer</ets>, squire), LL. <ets>scuria</ets>, OHG. <ets>skiura</ets>, <ets>sc<?/ra</ets>, barn, shed, G. <ets>scheuer</ets>, from a root meaning <ets>to cover</ets>, <ets>protect</ets>, and akin to L. <ets>scutum</ets> shield. See <er>Esquire</er>, and cf. <er>Ecurie</er>, <er>Querry</er>.]</ety>

<p><b>1.</b> <def>A large stable or lodge for horses.</def>

<i>Johnson.</i>

<p><b>2.</b> <def>An officer of princes or nobles, charged with the care of their horses.</def>

<note>&hand; In England <i>equerries</i> are officers of the royal household in the department of the Master of the Horse.</note>

<h1>Equery</h1> <Xpage=504>

<hw>Eq"ue*ry</hw> <tt>(?)</tt>, <tt>n.</tt> <def>Same as <er>Equerry</er>.</def>

<h1>Equestrian</h1> <Xpage=504>

<hw>E*ques"tri*an</hw> <tt>(?)</tt>, <tt>a.</tt> <ety>[L. <ets>equester</ets>, from <ets>eques</ets> horseman, fr. <ets>equus</ets> horse: cf. F. <ets>\'82questre</ets>. See <er>Equine</er>.]</ety>

<p><b>1.</b> <def>Of or pertaining to horses or horsemen, or to horsemanship; <as>as, <ex>equestrian</ex> feats, or games</as>.</def>

<p><b>2.</b> <def>Being or riding on horseback; mounted; <as>as, an <ex>equestrian</ex> statue</as>.</def>

<blockquote>An <b>equestrian</b> lady appeared upon the plains. <i>Spectator.</i></blockquote>