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name in its limited sense was applied to the coast extending from the river Hermus to the promontory of Lectum, on the north side of the entrance to the Gulf of Adramyttium, and lying between Ionia to the S. and Troas to the N. In its wider acceptation it comprehended Troas and the coasts of the Hellespont to the Propontis, where there were likewise several Æolian colonies.

Æolus, in Heathen Mythology, the god and father of the winds, was variously represented as the son of Hippotes, or of Nepture by a daughter of Hippotes, or of Jupiter. In the Odyssey he is mentioned as the king of the Æolian isle to whom Jupiter had given the superintendence and distribution of the winds. Later poets make him the god and father of the winds, who dwelt in one of the Æolian islands—according to some in Stromboli, according to others in Lipari, while others place his residence at Rhegium in Italy. He is represented as having authority over the winds, which he confined 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.

Through Hippotes, Æolus is usually represented as descended from Æolus, one of the sons of Hellen, and the mythological ancestor of the Æolian tribes.

Æon (αἰών), a space of time, was often used in Greek to denote indefinite or infinite duration; and hence, by metonymy, for a being that exists for ever. In the latter sense it was chiefly used by the Gnostic sects to denote those eternal beings or manifestations which emanated from the one incomprehensible and ineffable God. See Gnosticism.

Æpinus, Franz Maria Ulrich Theodor, a distinguished German natural philosopher, was born at Rostock in Saxony in 1724, and died at Dorpat in August 1802. He was descended from John Æpinus (b. 1499—d. 1553), the first to adopt the Greek form (αἰπεινός) of the family name, a leading theologian and controversialist at the time of the Reformation. After studying medicine for a time, Francis Æpinus devoted himself to the physical and mathematical sciences, in which he soon gained such distinction that he was admitted a member of the Berlin Academy of Sciences. In 1757 he settled in St Petersburg as member of the Imperial Academy of Sciences and professor of physics, labouring there and pursuing his favourite studies with great success till his death. He enjoyed the special favour of the Empress Catharine II., who appointed him tutor to her son Paul, and endeavoured, without success, to establish normal schools throughout the empire under his direction. Æpinus is best known by his researches, theoretical and experimental, in electricity and magnetism. His principal work, Tentamen Theoriæ Electricitatis et Magnetismi, published at St Petersburg in 1759, may be regarded as the first systematic and successful attempt to apply mathematical reasoning to these subjects. Adopting Franklin's theory of positive and negative electricities, or electric forces, he investigated the relations of these fully, and especially the conditions of their equilibrium; and many of the conclusions he arrived at do not depend for their value and importance on the theory of Franklin. Æpinus himself extended the theory, holding that the particles of the electric fluid repel each other, attract the particles of all bodies, and are attracted by them, with a force inversely proportional to the distance; that the fluid inversely proportional to the distance; that the fluid resides in the pores of the surfaces of bodies, moving readily through some, called conductors or non-electrics, and with difficulty through others; and that electric phenomena are produced either by the approach of bodies unequally charged, or by the unequal distribution of the fluid in the same body. He propounded a kindred theory of magnetism, a magnetic fluid being supposed to exist corresponding to the electric fluid, but acting on, and acted on by, the particles of iron only. It is to be added that Æpinus was the first to perceive and define, with any measure of clearness, the affinity between electricity and magnetism. There is a remarkable similarity between portions of the work above named and a paper by Cavendish—the result of independent investigations—given in the Philosophical Transactions for 1771. In 1787 the Abbé Haüy published an exposition of Æpinus's theories. Æpinus did not confine himself to one or two departments of natural science. He published a treatise, in 1762, On the Distribution of Heat at the Surface of the Earth; and he was also the author of valuable memoirs on different subject in astronomy, mechanics, optics, meteorology, and pure mathematics, contained in the journals of the learned societies of St Petersburg and Berlin. His discussion of the effects of parallax in the transit of a planet over the sun's disc excited great interest, having appeared (in 1764) between the dates of the two transits of Venus that took place during last century.

Æqui, an ancient and warlike people of Itality, 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 302 B.C.

Ærarians, a class in ancient Rome, composed of citizens who had suffered the severest kind of degradation the censors could inflict, but concerning whose exact position we have no precise information. Though heavily taxed, they did not enjoy the rights of citizenship beyond their liberty and the general protection of the state. They could not vote in assemblies or serve in the army, and were deprived of and excluded from all posts of honour and profit. Romans of the higher classes, as well as the plebians, were liable to become Ærarians. The name may be derived from æs, æris, money, since they were mere tax-payers; or, which is more probable, it may refer to the list of them which the censors gave in to the ærarium or public treasury.

Ærarium, the public treasury at ancient Rome. It contained the moneys and accounts of the state, and also the standards of the legions, the public laws engraven on brass, the decrees of the senate, and other papers and registers of importance. The place where these public treasures were deposited, from the time of the establishment of the republic, was the temple of Saturn, on the eastern slope of the Capitoline hill. In addition to the common treasury supported by the general taxes and charged with the ordinary expenditure, there was a reserve treasury, also in the temple of Saturn, the ærarium sanctum (or sanctius), maintained chiefly by a tax of 5 per cent. on the value of all manumitted slaves, which was not to