a town with 6383 inhabitants, in the arrondissement of Ghent, and province of East Flanders.

ÆLURUS, the Latinised Greek name of the cat deity of Egypt; represented sometimes like a cat, and sometimes as a human body with a cat's head. The Egyptians had so superstitious a regard for this animal, that the killing of it, whether by accident or design, was punished with death; and Diodorus relates, that, in a time of famine, they chose rather to eat one another than touch these sacred animals. The cat was sacred to the goddess Pasht or Bubastis.

ÆMILIUS L. PAULLUS, son of that L. Paulus Emilius who was killed at the battle of Cannae. He was twice consul. In his first consulate he triumphed over the Ligurians, and in the second subdued Perseus, king of Macedon, and reduced that country to a Roman province, for which he obtained the surname of Macedonicus. He died B.C. 160, at the age of seventy.

ÆMILIUS, Paulus, or Paolo Emilio, a celebrated historian, born at Verona, who obtained such reputation in Italy, that he was invited into France by the cardinal of Bourbon, in the reign of Louis XII., in order to write the history of the kings of France in Latin, and was presented to a canonry in the cathedral of Paris. He died at Paris on the 5th of May 1529. His work entitled De Rebus gestis Francorum was translated into French by Renard in 1581, and has also been translated into Italian and German.

ÆMOBOLIUM, in Antiquity, the blood of a bull or ram offered in the sacrifices, called taurobolia and criobolia; in which sense the word occurs in ancient inscriptions.

ÆNEAS, in Fabulous History, a Trojan prince, the son of Venus and Anchises. He plays a conspicuous part in the Iliad, and is represented, along with Hector, as the chief bulwark of the Trojans. Virgil has chosen him as the hero of his great epic, and the story of the Æneid, though not only at variance with other traditions, but inconsistent with itself, can never lose its place as a biography of the mythical founder of the Latin power. Æneas is described in the Æneid as escaping from the destruction of Troy, bearing his aged father on his shoulders, carrying in one hand his household gods, while with the other he leads his little son Ascanius or Iulus. His wife Creusa is separated from them and lost in the tumult. After a perilous voyage he lands in Africa, and is kindly received by Dido, queen of Carthage; who, on his forsaking her to seek a new home, destroys herself. Again escaping the dangers of the sea, he arrives in Italy, where he forms an alliance with Latins, a prince of the country, marries his daughter Lavinia, and founds a city which he calls after her, Lavinium. Turnus, king of the Rutuli, a rejected suitor of Lavinia, makes war on Latins, and both are slain in battle. Æneas assumes the sovereignty of Latium, and the Trojan and Latin powers are united in one nation. After a reign of three years, Æneas falls in a battle with the Rutuli, assisted by Mezentius, king of Etruria, and is carried up into heaven.

ÆNEAS SYLVIIUS, Pope. See PIUS II.

ÆNEID, the name of Virgil's epic poem, in celebration of the settlement of Æneas in Italy. See VIRGIL.

ÆNIGMA denotes any dark saying, wherein some well-known thing is concealed under obscure language. The word is Greek, Ανεγκα, from αναρροφησις, obscure inuere, to hint a thing darkly (ανεγκα, a tale, saying, or proverb). The popular name is riddle; from the Belgic raeden, or the Saxon arædan, to interpret.

Painted Ænigmas are representations of the works of nature or art, concealed under human figures, drawn from history or fable.

A Verbal Ænigma is a witty, artful, and abstruse description of anything. In a general sense, every dark saying, every difficult question, every parable, may pass for an enigma. Hence obscure laws are called ænigmata juris. The alchemists are great dealers in the enigmatic language, their processes for the philosopher's stone being generally wrapt up in riddles: e.g. Fac ex more et feminam circulum, inde quadrangulum, hinc triangulum, fac circulum, et habeas lapidem philosophorum.

ÆNTHOLOGIUS, in Poetry, a verse of two dactyls and three trochei; as Praetia dira placent truci juvente.

ÆOLIE INSULE, now Isole di Lipari, in Ancient Geography, seven islands situate between Sicily and Italy; so called from Æolus, the god of the winds, who was supposed to have ruled there. The Greeks call them Hephaestides; and the Romans Vulcaniae, from their fiery eruptions. They are also called Lipareorum Insulae, from their principal island Lipari. Dionysius Periegetes calls them Ædoroi, because circumnavigable.

ÆOLIAN HARP, a musical instrument consisting of catgut strings stretched over a wooden sound-box. When exposed to a current of air, the strings produce a variety of pleasing harmonic sounds in wild succession and combination. See Music.

ÆOLIC, in a general sense, denotes something belonging to Æolis.

Æolic, or Æolian, in Grammar, denotes one of the five dialects of the Greek tongue. It was first used in Boeotia, whence it passed into Æolia, and was that in which Sappho and Alcaeus wrote. The Æolic dialect generally throws out the aspirate or sharp spirit, and agrees in so many things with the Doric dialect, that the two are usually confounded.

The Æolic digamma is a name given to the letter F, which the Æolians used to prefix to words beginning with vowels, as Φουος for φυος; also to insert between vowels, as οφις for οφις.

Æolic Verse, in Prosody, a verse consisting of an iambus ÆOLIPILE or spondeae; then of two anapaests, separated by a long syllable; and, lastly, of another syllable: such as, O stelliferi conditor orbis. It is also called eulogic verse; and, from the chief poets who used it, Archilochean and Pindaric.

ÆOLIPILE, in Hydraulics, is a hollow ball of metal, generally used in courses of experimental philosophy, in order to demonstrate the possibility of converting water into an elastic steam or vapour by heat. The instrument, therefore, consists of a slender neck or pipe, having a narrow orifice inserted into the ball by means of a shouldered screw. This pipe being taken out, the ball is filled almost full of water and the pipe being again screwed in, the ball is placed on a pan of kindled charcoal, where it is well heated, and there issues from the orifice a vapour, with prodigious violence and great noise, which continues till all the included water is discharged. The stronger the fire is, the more elastic and violent will be the steam; but care must be taken that the small orifice of the pipe be not by any accident stopped up, because the instrument would in that case infallibly burst in pieces, with dangerous violence. Another way of introducing the water is to heat the ball red-hot when empty, which will drive out almost all the air; and then, by suddenly immersing it in water, the pressure of the atmosphere will force in the fluid, till it is nearly full. Descartes and others have used this instrument to account for the natural cause and generation of the wind: and hence it was called Æolipila: q. d. pilæ Æolii, the ball of Æolus.

ÆOLIS, or ÆOLIA, in Ancient Geography, a country of Asia Minor, settled by colonies of Eolian Greeks. Taken widely, it comprehends all Troas and the coast of the Hellespont to the Propontis, because in those parts there were several Æolian colonies. In a more limited sense it is applied to the district between Troas to the N. and Ionia to the S.

ÆOLUS, in Heathen Mythology, the god of the winds, was said to be the son of Jupiter by Acasta or Sigesia, the daughter of Hippotas; or, according to others, the son of Hippotas by Menecles, daughter of Hyllus, king of Lipara. He dwelt in the island now called Stromboli, one of the Æolian islands. Others place his residence at Rhegium, in Italy; and others, again, in the island Lipara. He is represented as having authority over the winds, which he held enchained in a vast cavern. Strabo, and some other writers, consider him to have had a real existence; and derive the fable of his power over the winds, from his skill in meteorology and the management of ships.

Hic vasto rex Æolus antro, Luctantis ventos tempestatisque sonoras Imperio premit, ac vincit et carcere frenat. Illis indignantes magno cum murmure montis Circumdantem utra fremitur; celèb sit æolus area Sceptris tenens, quæstiones animos, et temperat iram: Ni faciat, maris ac terras columque profundum Quippe ferant rapidi secum, verraque per auras.

ÆNEID, Lib. I. 52.

ÆON, a Greek word, properly signifying the age or duration of any thing.

Æon, among the followers of Plato, was used to signify any virtue, attribute, or perfection: hence they represented the deity as an assemblage of all possible æons, and called him pleroma, a Greek term signifying fulness. The Valentinians, who, in the first ages of the church, blended the conceits of the Jewish cabalists, the Platonists, and the Chaldean philosophers, with the simplicity of the Christian doctrine, invented a kind of Theogony, or Genealogy of Gods (not unlike that of Hesiod), whom they called by several glorious names, and all by the general appellation of Æons: among which they reckoned Zæon, life; Λόγος, word; Μονογενής, only-begotten; Παντοκράτωρ, fulness; and many other divine powers and emanations, amounting in number to thirty; which they fancied to be successively derived from one another, and all from one self-originated deity, named Bythus, i.e. profound or unfathomable; whom they called likewise, the most high and ineffable father.

ÆORA, among ancient writers on medicine, is used for gestation; which sort of exercise was often prescribed by the physicians of those days. Other exercises consisted principally in the motion of the body; but in the æora the limbs were at rest, while the body was carried about and moved from place to place, in such a manner as the physician prescribed. It had therefore the advantage of exercise, without the fatigue of it. This exercise was promoted several ways; sometimes the patient was laid in a sort of hammock, supported by ropes, and moved backward and forward; sometimes his bed ran nimbly on its feet; and sometimes he was carried in a litter, in a boat or ship, or on even ground in a chariot. Asclepiades was the first who brought gestation into practice, which was used as a means to recover strength after a fever, &c.

ÆPINUS, FRANCIS ULRICH THEODOR, eminent in the mathematics, and in natural philosophy, was born at Rostock in Lower Saxony in 1724, and died at Dorpt in Livonia in 1802. We regret that our means of information did not enable us to communicate any particulars in regard to his personal history; but we shall give some account of his contributions to science; and these, after all, form the most interesting memorials of a philosopher's life.

The work by which he is best known is entitled Tentamen Theoria Electricitatis et Magnetismi, published at Petersburg in 1759. It appeared under the sanction of the Imperial Academy, to which the theory had been in part communicated; and it is said on the title-page to be Instaur Supplementi Comment. Acad. Petropolitanae. The work indeed merited this distinction, as being the first systematic and successful attempt to apply mathematical reasoning to the subjects of electricity and magnetism. Already the theory of Franklin with regard to the former was very generally received, and was supposed to afford a satisfactory explanation of the phenomena. But though it seemed sufficient for this purpose in the common and somewhat loose manner in which the matter had hitherto been treated, it was not certain that the same would hold when the conclusions were accurately and mathematically deduced. To apply this test was what Æpinus undertook, and what he has executed in a manner very satisfactory and complete. He has treated very fully, and perhaps has nearly exhausted, what may be called the statics of electricity and magnetism, or the equilibrium of their forces. A great field yet remains, where the motion of the electric fluid is to be considered, and its distribution over the surfaces of bodies of a given figure; where greater difficulties are to be encountered, and where the latest improvements of the integral calculus in the hands of Laplace and Poisson have begun to be applied. The investigations of Æpinus in their own department led to very satisfactory results, and the exact agreement between them and the phenomena actually exhibited was extensively observed. Notwithstanding this agreement, we cannot consider the theory of positive and negative electricity as being yet sufficiently established. Though the assumption on which it is founded appear very simple at first, it is found more complex on a nearer inspection. The assumption is, that a fluid resides in the surfaces of all the bodies termed electrics, which is highly elastic, and strongly attracted, at the same time, by the particles of the body; and that while this fluid remains equally diffused over the surface of the body, no phenomenon whatever gives any information of its existence. By certain mechanical opera- Æpinus, however, the equilibrium of this fluid may be destroyed; the fluid may be accumulated at one end, or on one side of a body, and entirely withdrawn from the opposite. It is when an electric is brought into this state that it exhibits the phenomena of electricity, between which and the calculus instituted on the suppositions just laid down, Æpinus has everywhere remarked the most exact agreement. One great difficulty, however, still remains: the negative ends of two electrified bodies repel one another just as much as the ends which are reckoned positive. But such an effect cannot result from the mere absence of a substance: when the electric fluid is withdrawn, if repulsion still continue, it must arise from the mutual action of the particles of the body itself. Thus it would appear, that, in the absence of the electric fluid, the tendency of the particles of matter is to repel one another. This is an essential part of the theory; and it is not accurate to say, that the doctrine of Franklin or Æpinus supposes no more than the existence of an elastic fluid diffused over the surfaces, and strongly attracted by the particles, of bodies. It supposes, besides, that those particles, in the absence of this fluid, mutually repel one another. This not only takes away from the simplicity of the hypothesis, but it is obviously a very unnatural, not to say a contradictory supposition; because, when the electric matter is removed, how comes it to pass that the particles of the body, notwithstanding their mutual repulsion, still cohere together as firmly as before? This difficulty is acknowledged by Æpinus himself; but it would seem that the theory had taken a strong hold of his mind before he was aware of this consequence from it, so that he became by degrees reconciled to a supposition which appeared to him at first not a little incongruous. This must not surprise us: it is not always that, even among philosophers, we meet with the candour, or perhaps we should say the courage, with which Newton suspended his belief in his own great discovery, the principle of universal gravity, as long as the erroneous opinion then existing about the magnitude of the earth made the moon's motion in her orbit appear inconsistent with the descent of falling bodies.

Another remark, made by Æpinus himself, involves in it a difficulty which should have induced him to view his theory with considerable diffidence. Though he considers the difference of the two electricities to be the same as between excess and defect, or to consist in this, that the fluid which is deficient in the one part is in excess in the other, he admits that no phenomenon points out on which side the excess, or on which the defect lies. This is a strong indication that the difference is not of the kind supposed. We are not left at a loss to tell whether cold is the absence of a substance which we call heat, or heat the absence of a substance which we call cold. If there were just as much reason for asserting the one of these propositions as the other, one would certainly be inclined to reject both. The same should be done with respect to electricity and magnetism.

The investigations of Æpinus, however, are by no means rendered useless, even if the theory of positive and negative electricity, or of positive and negative magnetism, be exchanged for that of two elastic fluids, each attracting the other, and both attracted by the particles of bodies. Most of his investigations may be easily accommodated to this supposition, and, therefore, they are, fortunately for themselves and for their author, of a more permanent nature than the principles from which they were deduced.

It is to be added to this, that Æpinus was the first who saw the affinity between electricity and magnetism in its full extent, and perceived the light that these two mutually cast on one another. He instituted a regular series of experiments on the nature of the tourmaline, on which he wrote a small treatise, published in 1762. He is to be regarded also as the inventor of the condenser of electricity, and of the electrophorus, of which he gave the complete theory.

A very excellent view of the theory of Æpinus was published at Paris by M. Haüy in 1787, in 8vo. The same author has, however, adopted the theory of the two fluids in his own treatise, *Leçons de Physique*. There is a remarkable coincidence between Æpinus's work on electricity and magnetism, and that of Mr Cavendish, given in the *Philosophical Transactions* for 1771, p. 584. The principles from which they set out, and the conclusions at which they arrive, are in a great measure the same. It appears, however, quite certain, that Mr Cavendish knew nothing of the work of the Russian philosopher till his own was completed. His mode of proceeding is more geometrical, and in some parts he has gone farther.

The researches of Æpinus were not confined to the subjects now mentioned, but extended to most of the branches of natural philosophy. Beside the treatise on the tourmaline, he published, in 1762, a work, in 4to, *On the distribution of heat at the surface of the earth*; a work which, though translated into French, has hardly, we believe, made its way into this country, and of which we are therefore unable to speak from our own knowledge. He is also the author of many valuable memoirs on different subjects in pure mathematics, in astronomy, mechanics, optics, meteorology, contained in the 7th, 8th, 9th, 10th, and 12th volumes of the *Novi Commentarii Petropolitanus*, and in the volumes of the *Berlin Memoirs* for 1755, 1756. In a memoir contained in the last of these, is the first account of his experiments on the tourmaline, which were conducted with great accuracy and judgment, and do honour to the author as a man of a sound and philosophical understanding, well instructed in the true principles of inductive investigation. Indeed, notwithstanding the objections we have made to his theories of electricity and magnetism, we must acknowledge that this is the general impression produced by the perusal of his works. He appears to have been well acquainted with practical astronomy, and sometimes to have had the charge of the imperial observatory. He made improvements on the micrometer and the reticulum, and wrote a memoir on the effects of parallax in the transit of a planet over the sun; a difficult subject, and one rendered at that time (1764) peculiarly interesting, on account of the transit of Venus which was just past, and that which was soon expected. (*Novi Com. Pet.* tom. x. p. 433.) In the same volume he has a memoir on the subject of accidental colours, which at that time had hardly been treated of by any author but Buffon; and another on the affinity between electricity and magnetism. In the 12th volume he notices, we believe for the first time, the electric property of the Brazilian emerald. He was not aware that this emerald is in reality the green tourmaline (*Broginiar*), tom. i. p. 418;) a variety of that mineral on which he had already exercised his ingenuity with so much success.

It is rare, in an advanced state of science, to have the satisfaction of making a new discovery with regard to a subject quite elementary, and one that has been long a subject of attention. This, however, happened to Æpinus with respect to the lever, and to the simplest kind of lever—that which has equal arms; of which he has demonstrated a new property, in the 8th volume of the *Commentaries* above referred to. It is this—If a lever with equal arms be acted on at its opposite ends by forces in a given ratio to one another, and having their directions parallel to straight lines given in position; and if these forces be resolved each into two, one at right angles to the lever, and the other in the direction of it; in the case of equilibrium, the sum of the two forces, having the same direction with the lever, will be the greatest possible. This theorem, remarkable for its simplicity, and for illustrating the connection between the equilibrium of bodies, and certain problems concerning the maxima or minima of variable quantities, occurred when he was pursuing some of his inquiries concerning magnetism. He seems not to have been very fortunate, however, in his investigation, which is more complex than is necessary, as the proposition admits of a geometrical demonstration remarkable for its simplicity. (J.P.)

ÆQUI, a brave ancient people of Italy, inhabiting the upper valley of the Anio, who, in confederacy with the Volsci carried on a long series of hostilities with the early Romans; but were finally subdued in the year B.C. 302.

ÆQUIMELIUM, in Antiquity, a place in Rome where stood the house of Spurius Macius, who, by largesses corrupting the people, affected the supreme power. Refusing to appear before the dictator Cincinnatus, he was slain by Servilius Ahala, master of the horse; his house was razed to the ground, and the spot on which it stood was called Area Æquimelii.—Livy, iv. 13-16.

ÆRA, in Chronology, a fixed point of time from whence any number of years is begun to be counted. It is sometimes also written in ancient authors Era. The origin of the term is contested, though it is generally allowed to have had its rise in Spain. Sepulveda supposes it formed from A.E.R.A., the note or abbreviations of the words annus erat Augusti, occasioned by the Spaniards beginning their computation from the time their country came under the dominion of Augustus, or that of receiving the Roman calendar. This opinion, however ingenious, is rejected by Scaliger, not only on account that in the ancient abbreviations A never stood for annus, unless when preceded by V for vicis; but that it seems improbable they should put ER for erat, and the letter A, without any discrimination, both for annus and Augustus. Vossius nevertheless favours the conjecture, and judges it at least as probable as either that of Isidore, who derives æra from æs, the tribute-money wherewith Augustus taxed the world; or that of Scaliger himself, who deduces it likewise from æs, though in a different manner. As he observes, was used among the ancients for an article or item in an account; and hence it came also to stand for a sum or number itself. From the plural æra, came the corruption æra, æ, æram, in the singular; much as Ostia, æ, Ostianum, the name of a place, from Ostia, the mouths of the Tiber.

The difference between the terms æra and epoch is, that the æras are certain points fixed by some people or nation, and the epochs are points fixed by chronologists and historians. The idea of an æra comprehends also a certain succession of years proceeding from a fixed point of time, and the epoch is that point itself. Thus the Christian æra began at the epoch of the birth of Jesus Christ. See Chronology.

ÆRARlUM, the treasury or place where the public money was deposited amongst the Romans.

ÆRARlUM Hithyæ, or Junonis Lucinae, was where the moneys were deposited which parents paid for the birth of each child.

ÆRARlUM Privatum was the emperor's privy purse, or the place where the money arising from his private patrimony was deposited.

ÆRARlUM Sanctus contained the moneys arising from the twentieth part of all legacies; this was kept for the extreme necessities of the state.

ÆRARlUM Vicesimarum, the place where the money arising from the taxes levied from foreign countries was laid up; so called because it most commonly consisted of a twentieth part of the produce.

There are several other treasuries mentioned in history, as the Ærarium Joventutis, Venusis, &c. The temple of Saturn was the public treasury of Rome, either because Saturn first taught the Italians to coin money, or, which is most likely, because this temple was the strongest and most secure, and therefore the fittest place for that purpose.

Ærarium differs from Fiscus, as the first contained the public money, the second that of the prince. The two are, however, sometimes indiscriminately used for each other.

ÆRARIUS, a name given by the Romans to a degraded citizen, who had been struck off the list of his century. Such persons were so called, because they were still liable to all the taxes (œra), though deprived of the privileges of citizens.

The œrarii were incapable of making a will, of inheriting, of voting in assemblies, or of enjoying any post of honour or profit; in effect, they were only subject to the burdens, without the benefits of society; yet they retained their freedom, and were not reduced to the condition of slaves. To be made an œrarius was a punishment inflicted for some offence, and reputed one degree more severe than to be expelled a tribe, tribus moveri.

ÆRARlUS was likewise an officer instituted by Alexander Severus, for the distribution of the money given in largesses to the soldiery or people.

ÆRARlUS was also used for a person employed in coining or working brass. These are sometimes called œrarii fusiores. At other times, œrarius is distinguished from fusiœ; the former answering to what we now call coppersmiths, the latter to founders.

ÆRARlUS was also applied to a soldier who receives pay.

ÆRIA, or ÆRIA, in Ancient Geography, the ancient name of Egypt. The scholiast on Apollonius Rhodius says, that not only Thessaly, but Egypt, was called Ἡρα by the Greeks, which Eusebius also confirms; and hence Apollinaris, in his translation of the 114th Psalm, uses it for Egypt. Hesychius applies this name to Ethiopia.

AERIE. See AIRY.