AM, or AME, a liquid measure used in most parts of Germany, but different in different towns. The aem commonly contains 20 vertils, or 80 masses: that of Heidelberg is equal to 48 masses, and that of Wirtemberg to 160 masses.

ÆMILIUS, PAULUS, the son of Paulus Æmilius 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 Macedonia, and reduced that country to a Roman province, on which he obtained the surname of Macedonicus. He returned to Rome loaded with glory, and triumphed for three days. He died 168 years before Christ.

ÆMILIUS, Paulus, a celebrated historian, born at Ve- rona, 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 it 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 famous Trojan prince, the son of Anchises and Venus. At the destruction of Troy, he bore his aged father on his back, and saved him from the Greeks; but, being too solicitous about his son and household gods, lost his wife Creüsa in the escape. Landing in Africa, he was kindly received by Queen Dido; but quitting her coast, he arrived in Italy, where he married Lavinia, the daughter of King Latinus, and defeated Turnus, to whom she had been contracted. After the death of his father-in-law, he was made king of the Latins, over whom he reigned three years; but joining with the Aborigines, he was slain in a battle against the Tuscans. Virgil has rendered the name of this prince immortal, by making him the hero of his poem.

ÆNEAS SYLVIUS, Pope. See Pius II.

ÆNEATORES, in Antiquity, the musicians in an army, including those that played on trumpets, horns, &c. The word is formed from æneus, on account of the brazen instruments used by them.

ÆNEID, the name of Virgil's celebrated epic poem, devoted to celebrate the establishment of Æneas in Italy.

ÆNGIA, one of the islands of the Archipelago. It lies in the bay of Engia, and the town of that name contains about 800 houses and a castle; and near it are the ruins of a magnificent structure, which was formerly a temple.

ÆNIGMA denotes any dark saying, wherein some well-known thing is concealed under obscure language. The word is Greek, ἀνύγμα, formed of ἀντισκευα, obscure in- nuere, to hint a thing darkly, and of αὐγή, an obscure speech or discourse. 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 any thing. In a general sense, every dark saying, every difficult question, every parable, may pass for an enigma. Hence obscure laws are called enigma-ta 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 mare et feminam circumd, inde quadrangulum, hinc triangulum, fac circulum, et habebis lapidem philosophorum.

F. Menestrier has attempted to reduce the composition and resolution of enigmas to a kind of art, with fixed rules and principles, which he calls the philosophy of enigmatic images.

The Subject of an Ænigma, or the thing to be concealed and made a mystery of, he justly observes, ought not to be such in itself; but, on the contrary, common, obvious, and easy to be conceived. It is to be taken either from nature, as the heaven or stars; or from art, as painting, the compass, a mirror, or the like.

The Form of Ænigmas consists in the words which, whether they be in prose or verse, contain either some description, a question, or a prosopopoeia. The last kind are the most pleasing, inasmuch as they give life and action to things which otherwise have them not. To make an enigma, therefore, two things are to be pitched Ænigmas on which bear some resemblance to each other, as the sun and a monarch, or a ship and a house; and on this resemblance is to be raised a superstructure of contrarieties, to amuse and perplex. It is easier to find great subjects for enigmas in figures than in words, inasmuch as painting attracts the eye and excites the attention to discover the sense. The subjects of enigmas in painting are to be taken either from history or fable: the composition here is a kind of metamorphosis, wherein, e. g. human figures are changed into trees, and rivers into metals. It is essential to enigmas, that the history or fable under which they are presented be known to every body, otherwise it will be two enigmas instead of one; the first of the history or fable, the second of the sense in which it is to be taken. Another essential rule of the enigma is, that it only admits of one sense. Every enigma which is susceptible of different interpretations, all equally natural, is so far imperfect. What gives a kind of erudition to an enigma, is the invention of figures in situations, gestures, colours, &c. authorized by passages of the poets, the customs of artists in statues, basso-relievos, inscriptions, and medals.

As to the solution of enigmas, it may be observed, that those expressed by figures are more difficult to explain than those consisting of words, because images may signify more things than words can; so that to fix them to a particular sense, we must apply every situation, symbol, &c. and without omitting a circumstance. As there are few persons in history or mythology without some particular character of vice or virtue, we are, before all things, to attend to this character, in order to divine what the figure of a person represented in a painting signifies, and to find what agreement this may have with the subject whereof we would explain it. Thus, if Proteus be represented in a picture, it may be taken to denote incognitancy, and applied either to a physical or moral subject, whose character is to be changeable, e. g. an almanack, which expresses the weather, the seasons, heat, cold, storms, and the like. The colours of figures may also help to unriddle what they mean; white, for instance, is a mark of innocence, red of modesty, green of hope, black of sorrow, &c. When figures are accompanied with symbols, they are less precarious; these being, as it were, the soul of enigmas, and the key that opens the mystery of them.

ÆNIGMATOGRAPHY, or Ænigmatology, the art of resolving or making enigmas.

ÆNITHOLOGIUS, in Poetry, a verse of two dactyls and three trochei; as Praeë dira placent truci juventae.

ÆOLIAE INSULAE, now Isoli Lipari, in Ancient Geography, seven islands situated between Sicily and Italy; so called from Æolus, who reigned there about the time of the Trojan war. The Greeks call them Hephaestiades; and the Romans Vulcania, from their fiery eruptions. They are also called Lipareorum Insulae, from their principal island Lipara. Dionysius Periegetes calls them Πίλαραι, because circumnavigable.

ÆOLIAN HARP. See Acoustics, and Harp.

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 which Sappho and Alcaeus wrote in. 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 together.

The Æolic digamma is a name given to the letter F, which the Æolians used to prefix to words beginning with vowels, as Fovos for oves; also to insert between vowels, as eV, for ve.

ÆOLIC Verse, in Prosody, a verse consisting of an iambus or spondee; then of two anapests, separated by a long syllable; and, lastly, of another syllable: such as, O stelliferi conditor orbis. This is otherwise called eulogic verse; and, from the chief poets who used it, Archilochian 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 such violence as might greatly endanger the lives of the persons near it. 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. pila Æoli, the ball of Æolus, or of the god of the winds.

ÆOLIS, or ÆOLIA, in Ancient Geography, a country of the Hither Asia, settled by colonies of Æolian Greeks. Taken largely, 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 north and Ionia to the south. The people are called Æoles or Æoliti.

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 Menecele, daughter of Hyllus, king of Lipara. He dwelt in the island Strongyle, now called Strombolo, one of the seven islands called Æolian, from their being under the dominion of Æolus. Others say that his residence was at Rhegium, in Italy; and others, again, place him in the island Lipara. He is represented as having authority over the winds, which he held en-chained in a vast cavern, to prevent their continuing the devastations they had been guilty of before they were put under his direction.

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 Gene-alogy 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 Zōn, life; Λόγος, word; Μονογενής, only-begotten; Πληρωμα, 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 un-fathomable; 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 do 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 Ten-tamen 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 Instar 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 ful-ly, 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 mo-tion of the electric fluid is to be considered, and its dis-tribution 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 be-tween 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- Epist. tions, 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 Æpinus 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. Haiuy 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 Petropolitanae, 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 (Brognart, 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.

(A.)

ÆQUIMELIUM, in Antiquity, a place in Rome where stood the house of Spurius Melius, who, by largesses corrupting the people, affected the supreme power. Refusing to appear before the dictator Cincinnatus, he was slain by Servilius Ahalia, master of the horse; his house was razed to the ground, and the spot on which it stood was called Area Aquimelii. (Livy.)

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. ER. 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 Sealiger, not only on account that in the ancient abbreviations \( \overline{A} \) never stood for annus, unless when preceded by \( V \) for vivit; 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 Sealiger himself, who deduces it likewise from æs, though in a different manner. Es, 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 by corruption era, ærum, in the singular; much as Ostia, Ostian, the name of a place, from Ostia, the mouth 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 era 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.

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

ÆRARIIUM Ilithya, or Jérinon Lucina, was where the moneys were deposited which parents paid for the birth of each child.

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

ÆRARIIUM Sancti contained the moneys arising from the twentieth part of all legacies: this was kept for the extreme necessities of the state.

ÆRARIIUM Vicesimarium, 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 Juventutis, Veneris, &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.

ÆRARIIUS, 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 liable to all the taxes (æra), without enjoying any of its privileges.

The ærarii 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 ærarius was a punishment inflicted for some offence, and reputed one degree more severe than to be expelled a tribe, tribu moveri.

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

ÆRARIIUS was also used for a person employed in coining or working brass. These are sometimes called araria fuseres. At other times, ærarius is distinguished from fuser; the former answering to what we now call copper-smiths, the latter to founders.

ÆRARIIUS was also applied to a soldier who receives pay.

ÆRIA, or EERIA, in Ancient Geography, the ancient name of Egypt. The scholiast on Apollonius Rhodius says, that not only Thessaly, but Egypt, was called Hæg 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.

ÆRIANS, in Church History, a branch of Arians, who to the doctrines of that sect added some peculiar dogmas of their own; as, that there is no difference between bishops and priests,—a doctrine maintained by many modern divines, particularly of the presbyterian and reformed churches. The sect received its denomination from Aerius, an Armenian priest of the fourth century.

Fros ÆRIS, among alchemists, small scales procured from copper melted by a strong heat: it is sometimes used for ærugo or verdigris.