Fig. 10 Eolipyle.
Æolipilæ or Æolipȳlæ, Gr. (αἴολος, the wind; and πύλη, an orifice). A metal vase with a narrow orifice, which was filled with water and placed upon the fire, either to make the chimney draw better, or, according to Vitruvius, to show which way the wind blew.
Æolian Harp, Gr. A musical instrument that is played on by the wind passing over its strings.
Ærarium, R. (æs, money). The public treasury as distinguished from the private treasury of the Emperors (fiscus). Under the Republic the temple of Saturn served as the public treasury, and here were preserved the produce of the revenue, the public accounts and other public records. The army had a separate treasury of its own called ærarium militare, entirely distinct from the ærarium publicum. It was established by Augustus to provide for the special expenditure of the army.
Aerial perspective. The realization of the effect of intervening atmosphere in the distances of a landscape.
Æro, R. A basket made of rushes or broom, but still more commonly of osier, and used for conveying sand. It was employed by the Roman soldiery when at work on intrenchments, excavations, or fortifications, as may be seen from bas-reliefs; more particularly some of those which adorn the column of Trajan.
Æruca, R. (æs, bronze). A very brilliant green colour artificially made to imitate verdigris.
Ærugo, R. Verdigris, the same colour as æruca (q.v.), but obtained from oxide of bronze. It is difficult to establish a real distinction between the two terms, as Pliny gives the name of ærugo (the rust of bronze) to what Vitruvius calls æruca. It is probable, however, that æruca was a kind of verdigris obtained by artificial means, while ærugo was the natural verdigris. This has given rise to the two terms, which by many archæologists are confused together. Æruca, the artificial copper rust, formed by the action of wine refuse upon copper, is an acetate of copper (verdigris): while the genuine copper rust, Ærugo, is a carbonate of copper.
Ærumna, R. A kind of fork by which travellers carried their baggage over the shoulder. 2. An instrument of punishment for slaves. (See Furca.)