Agar′ic (Agarĭcus), a large and important genus of fungi, characterized by having a fleshy cap or pileus, and a number of radiating plates or gills on which are produced the naked spores. The majority of the species are furnished with stems, but some are attached to the objects on which they grow by their pileus. Over a thousand species are known, and are arranged in five sections according to whether the colour of their spores is white, pink, brown, purple, or black. The chief British representatives are the common wild mushroom (A. campestris, L.), the Horse mushroom (A. arvensis, Schæff.), A. elvensis, B. and Br., A. silvaticus, Schæff., &c. Many of the species are edible, like the common mushroom, and supply a delicious article of food, while others are deleterious and even poisonous.
Agaric Mineral, or Mountain-meal, one of the purest of the native carbonates of lime, found chiefly in the clefts of rocks and at the bottom of some lakes in a loose or semi-indurated form resembling a fungus. The name is also applied to a stone of loose consistence found in Tuscany, of which bricks may be made so light as to float in water, and of which the ancients are supposed to have made their floating bricks. It is a hydrated silicate of magnesium, mixed with lime, alumina, and a small quantity of iron.
Aga′sias, a Greek sculptor of Ephesus, about 400 B.C., whose celebrated statue, known as the Borghese Gladiator, representing a soldier contending with a horseman, is now in the Louvre, Paris.
Agassiz (ag′as-ē), Louis John Rudolph, an eminent naturalist, born 1807, died 1873, son of a Swiss Protestant clergyman at Motiers, near the eastern extremity of the Lake of Neufchâtel. He completed his education at Lausanne, and early developed a love of the natural sciences. He studied medicine at Zürich, Heidelberg, and Munich. His attention was first specially directed to ichthyology by being called on to describe the Brazilian fishes brought to Europe from Brazil by Martius and Spix. This work was published in 1829, and was followed in 1830 by Histoire Naturelle des Poissons d'eaux douces de l'Europe Centrale (Fresh-water Fishes of Central Europe). Directing his attention to fossil ichthyology, five volumes of his Recherches sur les Poissons Fossiles appeared between 1834 and 1844. His researches led him to propose a new classification of fishes, which he divided into four classes, distinguished by the characters of the skin, as ganoids, placoids, cycloids, and ctenoids. His system has not been generally adopted, but the names of his classes have been taken as useful terms. In 1836 he began the study of glaciers, and in 1840 he published his Études sur les Glaciers, in 1847 his Système Glaciaire. From 1838 he had been professor of natural history at Neufchâtel, when in 1846 pressing solicitations and attractive offers induced him to settle in America, where he was connected as a teacher first with Harvard University, Cambridge, and afterwards with Cornell University as well as Harvard. After his arrival in America he engaged in various investigations and explorations, and published numerous works, including: Principles of Zoology, in connection with Dr. A. Gould (1848); Contributions to the Natural History of the United States (4 vols., 1857-62); Zoologie Générale (1854); Methods of Study in Natural History (1863). In 1865-6 he made zoological excursions and investigations in Brazil, which were productive of most valuable results.
Agassiz held views on many important points in science different from those which prevailed among the scientific men of the day, and in particular he strongly opposed the evolution theory. Cf. Letters and Recollections, edited by G. R. Agassiz.
Agassiz (ag′a-sē), Mount, an extinct volcano in Arizona, United States, 10,000 feet in height; a place of summer resort, near the Great Cañon of the Colorado.
Ag′ate, a semi-translucent compound mineral mass formed in the cavities of rocks by the successive deposition of various types of silica, or by the staining of a siliceous mass thus deposited along concentric zones. Bands or layers of various colours blended together, the base generally being chalcedony, and this mixed with variable proportions of jasper, amethyst, quartz, opal, heliotrope, and carnelian. The varying manner in which these materials are arranged causes the agate when polished to assume some characteristic appearances, and thus certain varieties are distinguished, as the ribbon agate, the fortification agate, the zone agate, the star agate, the moss agate, the clouded agate, &c. In Scotland they are cut and polished under the name of Scottish pebbles.
Agathar′chus, a Greek painter, native of Samos, the first to paint a scene for the acting of tragedies. The view, however, that he applied the rules of perspective to theatrical scene-painting is doubtful. He flourished about 480 B.C.
Agath′ias, a Greek poet and historian, born at Myrina, Asia Minor, about A.D. 530; author of an anthology, a collection of love poems, and a history of his own times, which is our chief authority for the period 552-8, during which time the Byzantine army was struggling against the Goths, Vandals, and Franks.