EQUESTRIAN STATUE. 166 EQUINOCTIAL STORM. sauce are Unu of Gattemel: Donatello, in Padua, the first in modern art., and tl Bartolomeo Colleoai, before the Church of Santi Giovanni et Paolo in Venice, by And the finest of all. Among the finest equestrian statues in modem arl are those of Frederick the Great, by Rauch, in Berlin, and of reat, by Falconet, in Saint Petersburg. E QUIAN'GULAR i from Lat. oequus, equal mgli I . A figure is said to be equian- gular" if all of its angles are equal, as those of a jular polygon. Triangles which [uiangular are called similar; but lutually equiangular polygons are not simi- lar unless their corresponding sides are propor- tional. (See Similarity. ) A polyhedron is equi- ir when all its polyhedral angles arc equal, as in a cube. A spiral (q.v.) is called equi- r when the angle included between any radius vector and the tangent at its extremity is the same. This i- the characteristic property of the logarithmic spiral. EQ'UID^! (Nep-Lat. liom. pi., from equus, or Solidungula. The horses, a family of hoofed mammals of the suborder Peris sodactyla, containing only a small number of . which so nearly resemble each other that most zoologists agree in referring them to one genus, Equus, though some have put the asses in the separate genus Asinus. They are distinguished from cither quadrupeds by the concentration of the foot and toes, or the extraor- dinary development of the middle toe, which thus carries the whole weight, and is incased in n boot-like hoof. There are. however, two small protuberances ('splint' bones) on each side of both the metacarpal and metatarsal, or 'canon' bones, which represent the former existence of other toes. The Equidae have six incisors in each jaw. and six molars on each side in each jaw; the males have also two small canine teeth in the upper jaw, sometimes in both jaws, which are almost always wanting in the females. The molars of the Equidaj have square crowns, and are marked by the lamina; of enamel with ridges forming four crescents. The wearing down of these develops different patterns at different > the examination of which, in the in- cisors, a person may determine with considerable accuracy the age of a horse, i See plate illustrat- ing this under EOBSE.) There is a wide space D the canine teeth and the molars. The siomaeli of the' Equidae i- simple, bul the intes- ad 1 he caecum est remelj large ; the digestive organs thus exhibiting an adaptation very different from those of the ruminants, to the same kind of not easily assimilated food. Another distinctive peculiarity of the Equidse i . thai the f( ma les have I wo teal - lit uated on the puli.-.. between the thighs. The Equidae are now found in a truly wild stale only in Asia and I OSBJ] remains exis< in 1 he newel 1 10 1 formal ion- in great abundance in many pari - hi ii.ii h the < >ld W orld and the New and the wh ry history of 1 he Equidae has ablj worked out . i See I foRsi Eos • n i 'i in ire bj fa r t he most family. The quagga is The zebra seems incapable of useful have been made. it h horses in the hope that the hybrid might be aide to withstand the fly I q.V. I in South Africa ; but though the hybrids are easily obtained, and seem hardy, they cannot survive the bites of that terrible scourge. See Ass; House; Mule; Qi agga; Zebu . EQUILIBRIUM, Mechanical (Lat. (Equilib- rium, level position, from cequus, equal + libra, balance i. The condition of a body or of a system of bodies when there is no cliange in its motion; that is, there is no acceleration of any kind, either of translation or of rotation. The mathematical conditions are. therefore, that the resultant force in any direction is zero, and that the resultant moment of the forces around any axis is zero. Equilibrium is called -table, unstable, or neutral, depending upon the conse- quence of giving the body or system of bodies a small impulse; if the change which results from this impulse is decreased by the forces called into action by the motion, the equilibrium is stable; if it increases, the equilibrium is unstable; if it remains unchanged, it is neutral. Thus a body suspended at rest by a string is in stable equi- librium ; a knife balanced on its point is in un- stable equilibrium; a sphere lying on a smooth horizontal table is in neutral equilibrium. The use of the word equilibrium is extended also so as to include the condition of no apparent change in many other cases. A liquid is in equilibrium with its vapor if there is no longer any apparent evaporation or condensation. Thermal equilib- rium is the condition when there is no longer any change in temperature. See Mechanics. EQUIMULTIPLE. See Multiple. EQUINE ANTELOPE. A book-name for either the roan or the sable antelope (qq.v. ). See Blaueok and Plate of Antelopes. EQUIN1A. See Glanders. EQUINOCTIAL (Lat. orquinocl talis, from wquinoctium, equinox, from oequus, equal + nox, night). The celestial equator. (See Equator, Celestial.) The equinoctial points are those in which the equinoctial and the ecliptic intersect. See Ecliptic. EQUINOCTIAL STORM, or GALE. For at least three hundred years past whenever a severe storm occurs on the Atlantic coast of North America or Great Britain at the season of the equinox, either autumnal or vernal, it has been spoken of as 'the equinoctial storm' or gale, and there has sprung up a popular belief that such a severe storm is due at or near the date of the equinox. The fact is, however, that the stormy season of the year over the North Atlantic begins with August and continues with increasing sever- ity until "March or April, and there is no special ila or period more likely than another to be stormy. Of course numerous severe storms are recorded near these dates, such as those of Sep (ember 20, 167C; October 20, 1770; September 23, 1815; October 2. 1841; October 7. 1849, and September 8, 1809; all of them along the meri- can COOSt ; but it will be noticed that these dales have no close connection with the equinoctial date September 22d and there are not more than a dozen such in the course of two hundred years. The equinoctial storm is therefore simply a name given to the heaviest storm that happens I cur within a few weeks of (be dale of the equinox. For statistical details consult: Quar- terly Journal Royal Meteorological Society (Lon- don! 1884) ; I mi,, l States Monthly Weather Re- (Washington, 1891-1000) ; Loomis, Treatise
