EQU 



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EQU 



to be equably accelerated or retarded 

 when it is increased or decreased by 

 equal quantities in equal times. 



EQTJAL'ITY, a term of relation between 

 things equal in magnitude, quantity or 

 quality. The sign now commonly used 

 to express equality is = but some writers 

 use OC, and others . 



EQUANT, a circle in astronomy, for re- 

 gulating and adjusting certain motions 

 of the planetary bodies. 



E'QUATED BODIES, or Gunter's Scale ; two 

 lines which relate to the comparison of 

 the sphere and the regular bodies. They 

 are seldom given on modern scales. 



EOUA'TION, that disposition of quan- 

 tities by which one set is made equal to 

 another however differently expressed. 

 Thus 11. 16s. 6d. = 678d. is an equation, 

 so is t/"+y= a b+c d. Equations are 

 said to be literal when the quantities 

 are expressed by letters, and numerical 

 when the co-efficients of the unknown 

 quantities and the absolute terms are 

 given in numbers. They are simple, when 

 the unknown quantities enter only in 

 the first degree ; quadratic, when they 

 enter in the second degree ; cubic, when 

 they enter in the third degree, &c. (See 

 DEGREE.) In astronomy, the term equa- 

 tion is used to express the amount of 

 correction to be added to or subtracted 

 from the mean position of a heavenly 

 body to obtain its true position ; hence 

 equation of time denotes the difference be- 

 tween mean and apparent time, or it is 

 the quantity to be added to or subtracted 

 from the mean time, to find the true as- 

 tronomical time. The equation of time 

 arises from two causes, the eccentricity 

 of the earth's orbit, and the obliquity of 

 the ecliptic. Equation of payments is an 

 arithmetical process for finding the time 

 to pay at once several debts due at sun- 

 dry times, and bearing no interest till 

 after the time of payment, so that no loss 

 shall be sustained by either party. 



EQUA'TOR, Lat. cequator, the equalizer; 

 a great circle of the sphere, equally dis- 

 tant from the two poles of the world, and 

 dividing it into two hemispheres, the 

 northern and southern. It is called the 

 equator, because when the sun is in this 

 circle the days and nights are of equal 

 length in all parts of the world. For this 

 reason the celestial equator is also called 

 the equinoctial (q.v.), and when drawn 

 on maps and globes, it is called the equi- 

 noctial line, or simply the line. From 

 this circle, referred to the earth, are 

 reckoned the degrees of latitude, both 

 north and south. Epithet equatorial, as 

 the equitorial regions. 



EQUATO'RIAL, an astronomical instru- 

 ment contrived for keeping an object in 

 > iew for any length of time, notwith- 

 standing the diurnal motion. 



KUUERY, k from Fr . MCUTM l.Au'nuid 



E'CIUERRK, J stable. a. An officer of 



the royal household under the nutter of 

 horse. The equerries are five in number, 

 and ride in the leading coach on grand 

 occasions, and have a table provided for 

 them. 



E'QUES AURATCS, a knight bachelor 

 called auratus ; q. d., gilt, because an- 

 ciently none but knights were allowed to 

 beautify their habiliments of war with 

 gold. 



EQUES'TRIAN, from equus, a term now 

 chiefly used in the phrase equestrian sta- 

 tue, which is the representation of a per- 

 son on horseback. The equestrian games, 

 the ludi equestres of the Romans, wero 

 horse races of five kinds: the plain horse- 

 race, the chariot-race, the decursory race 

 about funeral piles, the ludi sevirales, and 

 the ludi neptunales. The equestrian order 

 was the second rank in Rome next to the 

 senators. 



EauiAN'ouLAR, having equal angles, 

 such as the square and all regular bodies. 

 The term is also applied to two or more 

 figures having equal angles. 



EQCICRO'RAL, from aquus, equal, and 

 cru, a leg ; having equal legs, but longer 

 than the base : isosceles. 



EQCIC'CLUS, \ the Horse's Head; a 



Eacus MI'NOR, > constellation of the 



EOUU'LEUS, j northern hemisphere, 

 representing, according to the poets, the 

 horse which Mercury pave to Castor, and 

 which he named Celeris. From the im- 

 perfect representation of the animal in 

 this constellation it has also been called 

 equi lectio. Number of stars 10. 



E'OCIDIF'FERENT, having equal differ- 

 ences : applied in arithmetic to any series 

 of quantities which proceed in arithmeti- 

 cal proportion, i.e. when the difference 

 between the first and second , the second 

 and third, the third and fourth, &c., terms 

 is the same, M 1 + 8 + ff + 7 t-9 -f- Ae., 

 is an equidifferent series. The term is also 

 applied to crystals when the faces of the 

 prism and each of the summits are dif- 

 ferent, but form a series, as 6. 4. 2. 



E'QUILAT'ERAL, from eequus, equal, and 

 latus, a side ; equal-sided. A bivalve is 

 said to be equilateral when a transverse 

 line drawn through the apex of the umbo 

 bisects the valve. An equilateral hyper- 

 bola has the two axes equal to one another. 



E'auitiB'RiuM (Lat.), equipoise; a term 

 used in mechanics for an equality offerees 

 acting in opposite directions, whereby 

 the body acted upon remains at rest, or 

 technically, in equlibrio. In fine arts, 

 equilibrium means the just poise or bal- 

 ance of an object, so as to appear to stand 

 firmly. 



E'auiMui/TiPLEs, products arising from 

 the multiplication of two or more primi 

 tive quantities by the same number o 





