EQU 



EQU 



equation ; if it contains the square of the 

 unknown quantity, it is called a quadratic 

 equation ; if the cube of the unknown 

 quantity, a cubic equation ; if the fourth 

 power, a biquadratic, &c. 



Equation, Quadratic. This is pure or 

 adfected. 1. Pure quadratic equations 

 are those which contain only the square 

 of the unknown quantity, as x^ = 36. 

 2. Adfected quadratic equations are those 

 which involve both the square and the 

 simple power of the unknown quantity, 

 as x^ + 4x = 45. 



EQUATION OF PAYMENTS. An 

 arithmetical rule for finding the mean 

 time for paying the amount of several 

 sums which are due at different times. 

 Rule: — Multiply each term by its time, 

 and divide the sum of the products by 

 the whole debt ; the quotient is accounted 

 the mean time. 



EQUATOR {ccquo, to make equal). 

 The Great Circle on the earth's surface, 

 every point in which is equally distant 

 from the poles. It divides the earth into 

 two equal parts, the one being called the 

 Northern, the other the Southern Hemi- 

 sphere. See Equinoctial. 



EQUATO'RIAL. An apparatus, for- 

 merly called a parallactic instrument, 

 used for all those astronomical observa- 

 tions which require an object to be kept 

 long in view. Its value consists in its 

 being capable, when once set upon an 

 object, of following the object for an inde- 

 finite period by a single motion, i. e. by 

 merely turning the whole apparatus 

 round on its polar axis. 



EQUATO'RIAL CURRENT. Adrift- 

 current which traverses the Atlantic 

 Ocean, named from its course lying under 

 or near the line. It is supposed to be 

 formed in the Bay of Benin, whence it 

 proceeds westward on both sides of the 

 equator, as far as 22° W. long. ; it then 

 declines somewhat southward towards 

 the Brazilian coast, and separates into 

 two currents, called the Guiana current 

 and the Brazil current. 



EQUIA'NGULAR {cequus angulus, 

 equal angle). As applied to a single 

 geometrical figure, the term denotes that 

 all its angles are equal, as in all regular 

 polygons; as applied to two figures of 

 the same kind, it denotes that the cor- 

 responding angles of the two figures are 

 equal, though, separately, they may not 

 be equiangular figures. 



E'QUIDiE {equus, a horse). The Horse 

 tribe; the solidungulous family of pachy- 

 dermatous animals, with only one ap- 

 125 



parent toe and a single hoof to each 

 foot. 



EQUILATERAL {cequa latera ha- 

 bens). A term applied to a geometrical 

 figure bounded by equal sides. 



EQUILI'BRIUM {ceque, equally, libro, 

 to poise). A term expressive of the 

 equable diffusion of temperature which 

 all bodies on the earth tend to produce ; 

 and of the equal distribution of the elec- 

 tric fluid in its natural undisturbed state. 

 Equilibrium of forces. When two forces 

 counteract, or balance each other, they 

 are said to be in equilibrio. To produce 

 this state in solid bodies, it is only neces- 

 sary to support the centre of gravity : a 

 pair of scales are in equilibrio, when the 

 beam is in a horizontal position. 



EQUIMULTIPLES. The products of 

 quantities multiplied by the same num- 

 ber. Thus six times A and six times B 

 are egwi-multiples of A and B; m'^np 

 and m* nq are equi-multiples of p and q; 

 a league and a yard are equimultiples of 

 a mile and a foot. 



EQUINO'CTIAL. A synonymous term 

 for the equator, because, when the sun 

 is in the plane of it, nodes cequantur, it 

 is equal day and night over the whole 

 world. 



EQUINO'CTIAL POINTS. The two 

 points of the ecliptic where the equi- 

 noctial or equator crosses it; viz., in the 

 first point of Aries and the first of Libra. 

 The times of the year answering to these 

 points are called Vernal and Autumnal 

 Equinoxes, the one happening in the 

 spring, the other in the autumn; the 

 vernal being that at which the sun 

 crosses the equinoctial from south to 

 north; the autumnal, when it quits the 

 northern and enters the southern hemi- 

 sphere. See Precession. 



EQUISETA'CEtE. Leafless branched 

 plants, with a striated fistular stem. In- 

 florescence consisting of peltate scales. 

 Reproductive bodies in the inside of the 

 lobes of the scales, consisting of four 

 club-shaped bodies, enveloping a naked 

 spore. 



EQUISETIC acid, a peculiar acid, 

 existing, in combination with magnesia, 

 in the Equisetum fluviatile. 



EQUIVALENTS, CHEMICAL {aquS, 

 equally, valeo, to avail). A term applied 

 by Wollaston to the combining propor- 

 tions of elementary and compound sub- 

 stances, as the quantities of acid and 

 base, in salts, required to neutralize each 

 other. The following are instances of 

 this law :— 



G3 



