AUT 



AXI 



many varieties of trap and volcanic 

 rocks. It is a silicate of lime and mag- 

 nesia. Augite rock is a particular kind 

 of trap rock, consisting of augite and 

 compact felspar, the former being pre- 

 dominant or in equal proportion. 



AURA ELECTRICA. A gale of elec- 

 tricity ; a term expressive of electricity, 

 as received from a point, from the sensa- 

 tion it communicates. 



AURA'NTlA'CEiE. The Orange tribe 

 of Dicotyledonous plants, abounding in 

 a volatile, fragrant, bitter, exciting oil. 

 Trees or shrubs with leaves alternate, 

 often compound, dotted with transparent 

 receptacles of volatile oil ; flowers poly- 

 petalous ; stamens hypogynous -, ovary 

 many-celled ; fruit pulpy, many-celled, 

 its rind filled with receptacles of oil. 



AURE'LIA {aurum, gold). Chrysalis. 

 A fanciful name for the nymph or pupa 

 state of insect life, from the glittering 

 spots of golden hue with which it is 

 sometimes speckled. 



AU'RIC ACID {aurum, gold). Auric 

 oxide. A name proposed by Pelletier 

 for the peroxide of gold, from its property 

 of forming salts with alkaline bases. 



AURI'CULATED {auricula, a little 

 ear). A term applied to a few bivalves 

 which have a flat angulated projection on 

 one or both sides of the umbones or 

 bosses. These processes are highly de- 

 veloped in the pecten, and are merely 

 an incipient modification of the hinge 

 margin in hyssoarca and several other 

 genera. The term is also applied, in 

 Botany, to leaves which have two 

 rounded lobes at the base. 



AU'RIFORM {auris, the ear, forma, 

 likeness). Ear-shaped ; as applied to the 

 haliotis among the mollusca. 



AURI'GA. The Charioteer ; a north- 

 ern constellation, consisting of sixty- 

 six stars, the principal of which is Ca- 

 pella. 



AURO'RA BOREA'LIS. Northern 

 Lights; Polar Lights, or Streamers. A 

 luminous meteor, generally appearing in 

 the northern part of the sky, and re- 

 sembling the Aurora, or morning twi- 

 light. It is usually referred to the 

 agency of electricity in the upper regions 

 of the atmosphere. 



AUSTRAL. The six signs of the zo- 

 diac, which are south of the equinoctial, 

 are called Austral signs. 



AUTHORITY. 1. This term is em- 

 ployed in its primary sense, when we 

 refer to any one's example, testimony, or 

 judgment ; in this sense it answers pretty 

 44 



nearly to the Latin auctoritas. 2. Some- 

 times it is employed as equivalent to 

 "potestas," power; as when we speak of 

 the authority of a magistrate. 



AUTO'MALITE. Fahlunite. A mi- 

 neral found in a talcose rock at Fahlun 

 in Sweden. Its constituent parts are 

 alumina, silica, and the oxides of zinc 

 and of iron. 



AUTOMA'TIC MOTIONS {airofMaro^, 

 self-moving). Those muscular actions 

 which are not dependent on the mind, 

 and which are either persistent, or take 

 place periodically with a regular rhythm, 

 and are dependent on normal causes 

 seated in the nerves or the central organs 

 of the nervous system. 



AUTUMN. The third quarter of the 

 year, which begins when the sun enters 

 Libra, that is, about tlie 21st or 22nd of 

 September, when the days and nights 

 are equal. 



AUTUMNAL EQUINOX. The time 

 when the sun enters Libra, or the de- 

 scending point of the ecliptic, called also 

 the Autumnal point. The signs Libra, 

 Scorpio, and Sagittarius, are called au- 

 tumnal signs. 



A'VALANCHE. A mass of snow 

 which, being detached from a great height 

 in the Alps, acquires enormous bulk 

 by accumulation as it descends. It is 

 termed, in the dialects of Switzerland, 

 lavange and lavanche. 



AVA'NTURINE. A variety of quartz 

 containing mica spangles. 



A'VES {avis, a bird). The fourth class 

 of the Vertebrata, or Encephalata, com- 

 prising birds; a class of oviparous ani- 

 mals, with warm blood, a double circula- 

 tion, a covering of feathers, and arms 

 constructed for flight. 



AVICU'LIDiE. Mussels and Pearl 

 Oysters ; a family of the atrachian bi- 

 valves, named from the genus avicula ; 

 the animal is attached, and byssifer- 

 ous ; the shells are lamellar, internally 

 perlaceous ; the valves generally gaping. 



AWN. A stiff bristle, formed by a 

 continuation of the midrib of a bract in 

 certain grasses, and commonly called the 

 arista or beard. 



AXE-STONE. A sub-species of jade, 

 used by the New Zealanders for making 

 hatchets. It is sometimes called Ama- 

 zonian stone, from its being found on the 

 banks of the river Amazon. 



AXI'LLA. The Latin term for the 

 arm-pit, and applied to other parts of the 

 animal body which form a similar angle. 

 In Botany, it denotes the angle made by 



