by a metal, salts are formed directly. An acid is therefore a salt, whose metal is hydrogen. The full importance of the definition of an acid will be learned under the heading Chemistry.
Acidalus, Valens a very distinguished scholar and critic, born in 1567 at Wittstock, in Brandenburg. After studying at Rostock and Helmstaedt, and residing about three years in Italy, he took up his residence at Breslau, where he professed the Roman Catholic religion. His excessive application to study was supposed to have caused his untimely death, which occurred in 1595, when he had just completed his twenty-eighth year. He wrote notes on Tacitus and Curtius, a commentary on Plautus, and a number of poems, which are inserted in the Deliciæ of the German poets. Baillet gave him a place among his Enfans Célèbres, and tells that he wrote the commentary on Plautus and several of the Latin poems when he was only seventeen or eighteen years of age.
Acinaces, an ancient Persian sword, short and straight, and worn, contrary to the Roman fashion, on the right side, or sometimes in front of the body, as shown in the bas-reliefs found at Persepolis. Among the Persian nobility they were frequently made of gold, being worn as a badge of distinction. The acinaces was an object of religious worship with the Scythians and others (Herod. iv. 62).
Acis, in Mythology, the son of Faunus and the nymph Symæthis, was a beautiful shepherd of Sicily, who being beloved by Galatea, Polyphemus the giant was so enraged that he crushed his rival with a rock, and his blood gushing forth from under the rock, was metamorphosed into the river bearing his name (Ovid, Met. xiii. 750; Sil. Ital. xiv. 221). This river, now Fiume di Jaci, or Acque Grandi, rises under a bed of lava on the eastern base of Etna, and passing Aci Reale, after a rapid course of one mile, falls into the sea. The waters of the stream, once celebrated for their purity, are now sulphureous.
Ackermann, John Christian Gottlieb, a learned physician and professor of medicine, born at Zeulenroda, in Upper Saxony, in 1756. At the early age of fifteen he became a student of medicine at Jena, where he soon attracted the favourable notice of Baldinger, who undertook the direction of his studies. When Baldinger was transferred to Göttingen in 1773, Ackermann went with him, and afterwards studied for two years at Halle. A few years' practice at Stendal (1778-99), where there were numerous factories, enabled him to add many valuable original observations to his translation of Ramazzini's Treatise of the Diseases of Artificers (1780-83). In 1786 he became professor of medicine at the university of Altorf, in Franconia, occupying first the chair of chemistry, and then, from 1794 till his death in 1801, that of pathology and therapeutics. Dr Ackermann's knowledge of the history of medicine may be estimated by his valuable contributions to Harless's edition of Fabricius' Bibliotheca Græca. He wrote numerous original works, besides translations.
Acœmetæ (ἀκοίμητος, sleepless), an order of monks instituted by Alexander, a Syrian, about the middle of the 5th century. Founding on the precept, Pray without ceasing, they celebrated divine service uninterruptedly night and day, for which purpose they divided themselves into three sections, that relieved each other in turn. The chief seat of the Acœmetæ was the cloister Studium at Constantinople, whence they were sometimes called Studites. Having adopted the monophysite heresy, they were put under the Papal ban about the year 536.
Acolyte (from ἀκόλονθος, an attendant), one of a minor order of clergy in the ancient church, ranking next to the sub-deacon. We learn from the canons of the fourth Council of Carthage that the archdeacon, at their ordination, put into their hands a candlestick with a taper and an empty pitcher, to imply that they were appointed to light the candles of the church and to furnish wine for the eucharist. Their dress was the cassock and surplice. The name and office still exist in the church.
Aconcagua, a province of Chile, South America, is about 100 miles long by 40 miles wide, and lies between 31° 30' and 33° 20' S. lat., and 70° and 71° 30' W. long., between the provinces of Valparaiso and Santiago on the N. and Coquimbo on the S. A large part of the province is mountainous, but it contains several rich and fertile valleys, which yield wheat, maize, sugar-cane, fruits, and garden produce in abundance. In the agricultural districts there are raised from 50 to 60 fanegas of wheat for every quadra, equal to about 35 bushels per English acre. The province has also mineral resources, but not to such extent as Coquimbo or Atacama. Its chief town is San Felipe. The mountain Aconcagua, one of the loftiest peaks of the Andes, rises to the height of 23,910 feet above the sea on the frontier between this province and Mendoza, a department of the Argentine Republic. A river of the same name rises on the south side of the mountain, and after a course of 230 miles falls into the Pacific 12 miles N. of Valparaiso. Population (1870), 134,178.
Aconite, Aconitum, a genus of plants commonly known as Aconite, Monkshood, Friar's Cap, or Helmet flower, and embracing about 18 species, chiefly natives of the mountainous parts of the northern hemisphere. They are distinguished by having one of the five blue or yellow coloured sepals in the form of a helmet; hence the English name. Two of the petals placed under the hood of the calyx are supported on long stalks, and have a hollow spur at their apex. The genus belongs to the natural order Ranunculaceæ, or the Buttercup family. Aconitum Napellus, common monkshood, is a doubtful native of Britain. It is an energetic irritant and narcotic poison. It causes death by a depressing effect on the nervous system, by producing palsy of the muscles concerned in breathing, and by fainting. A tincture prepared by the action of spirit on the roots is used medicinally to allay pain, especially in cases of tic. Its roots have occasionally been mistaken for horse-radish. The Aconite has a short underground stem, from which dark-coloured tapering roots descend. The crown or upper portion of the root gives rise to new plants. When put to the lip, the juice of the Aconite root produces a feeling of numbness and tingling. The horse radish root, which belongs to the natural order Cruciferæ, is much longer than that of the Aconite, and it is not tapering; its colour, is yellowish, and the top of the root has the remains of the leaves on it. It has a pungent taste. Many species of Aconite are cultivated in gardens, some having blue and others yellow flowers. Aconitum Lycoctonum, Wolfsbane, is a yellow-flowered species common on the Alps of Switzerland. One species, Aconitum heterophyllum, found in the East Indies, and called Butees, has tonic properties in its roots. The roots of Aconitum ferox supply the famous Indian (Nipal) poison called Bikh, Bish, or Nabee. This species is considered by Hooker and Thomson as a variety of Aconitum Napellus. Aconitum palmatum yields another of the celebrated Bikh poisons. Aconitum luridum, of the Himalayas, also furnishes a poison.
Acontius, the Latinised form of the name of Giacomo Aconico, a philosopher, jurisconsult, engineer, and theologian, born at Trent on the 7th September 1492. He embraced the reformed religion; and after having taken refuge for a time in Switzerland and Strasburg, he came to England about 1558. He was very favourably received by
