AUG 



A RG 



applied to a cluster of islands, especially 

 to those lying between the shores of 

 Greece and Asia Minor. The term is 

 perhaps derived from k'ifeiov TreXayu?, 

 Mgceum pelagus, the ^gean sea. 



A'RCTIC CIRCLE (cip/cTo?, a bear). 

 An imaginary line extending round the 

 North Pole, (jQ^ degrees from the equator, 

 and parallel to it. This, and the Antarc- 

 tic circle, are called the polar circles. 



A'RCTIC CURRENT. A current in 

 the North Atlantic, which seems to ori- 

 ginate in the extensive masses of ice 

 surrounding the North Pole, runs down 

 along the eastern shores of Greenland, 

 doubles the Cape, and runs up the west- 

 ern coast of Greenland, crosses Davis's 

 Strait, follows the coast of Labrador, runs 

 to the east of Newfoundland, and even- 

 tually joins the gulf stream between 43° 

 and 47° of longitude. 



A'RCTIC POLE (cipKTo?, a bear). A 

 designation of the North Pole of the 

 earth, from its pointing to the constella- 

 tions of the Great and Little Bears. 



ARCTU'RUS or a BOO'TES (ci/jKrof, 

 the bear, ovpa, the tail). A star of the 

 first magnitude in the northern constel- 

 lation Bootes. It is nearly in a right 

 line drawn through the two hinder stars 

 in the tail of the Bear. 



A'RCUATE {arcus, a bow). Curved 

 or arched ; a term applied, in Botany, to 

 any thing bent like the arc of a circle, as 

 the legume of medicago falcata, the em- 

 bryo of certain plants, &c. 



A'RDEID^ {ardea, the heron). The 

 Heron tribe ; a family of the Grallatores, 

 or wading birds, including the herons, 

 cranes, and storks, in which the beak is 

 long, thick, and stout, usually with cut- 

 ting edges as well as a point. 



A'REA. The Roman area was a 

 threshing-floor; but the term is em- 

 ployed by geometricians to denote any 

 superficies or surface of a determinate 

 extent, and is applied exclusively to 

 plane figures. 



A'REOLATE {areola, a little space). 

 Divided into areolae or small spaces, as 

 applied to surfaces. 



ARFWE'DSONITE. A ferruginous 

 variety of hornblende, named from Arf- 

 wedson. 



A'RGAL. Wine-sione. Crude tartar; 

 an acidulotis concrete salt, deposited on 

 the interior of wine-casks, and used by 

 dyers as a mordant. On being purified, 

 it is called cream or crystals of tartar. 



ARGAND LAMP. A lamp with a 

 hollow wick, for furnishing a rapid sup- 

 37 



ply of air to the interior as well as to the 

 exterior of the flame. It is named from 

 its inventor, who was a native of France. 



ARGILLA'CEOUS EARTH. Argilla. 

 White clay, or potters' earth; the earth 

 or clay, called by chemists alumina, 

 from its being obtained in its greatest 

 purity from alum. 



ARGILLA'CEOUS ROCKS {argilla, 

 clay). Homogeneous soft substances, 

 composed chiefly of aluminous earth, or 

 clay. They comprise the shale or slate- 

 clay, bituminous shale, clay, and marl. 



ARGI'LLITE {argilla, 'clay). Argil- 

 laceous schist, or clayslate; a mineral 

 abundantly distributed in both primitive 

 and transition mountains. 



ARGO NAVIS. The Ship ; a southern 

 constellation, containing sixty-four stars, 

 the principal of which is Canopus. 



A'RGUMENT. In Logic, an expres- 

 sion in which, " from something laid 

 down and granted as true {the premises), 

 something else {the conclusion) beyond 

 this must be admitted to be true, as fol- 

 lowing Necessarily from the other." 



I. The term Argument, in ordinary 

 discourse, has several meanings. 1. It 

 is very often used for the premises alone, 

 in contradistinction to the conclusion ; 

 e.g., "the conclusion which this argu- 

 ment is intended to establish is so and 

 so." 2. It is sometimes employed to de- 

 note what is, strictly speaking, a course 

 or series of such arguments, as when it 

 is applied to an entire dissertation. 

 3. Sometimes it signifies a disputation, 

 or two trains of argument, opposed to 

 each other. 4. Lastly, the various forms 

 of stating an argument are sometimes 

 spoken of as different kinds of argument, 

 as if the same argument were not capable 

 of being stated in various ways. — Whately. 



II. The term Argument, in astronomical 

 tables, denotes the angle or quantity on 

 which a series of numbers depends. If, 

 for instance, a table were formed of the 

 sun's declination, corresponding to every 

 degree, &c. , of longitude, so that, the longi- 

 tude being known, the declination might 

 be found opposite to it in the table, the 

 longitude would then be called the argu- 

 ment of the declination, and the table would 

 be said to be entered with the argument. 



ARGUME'NTUM AD HOMINEM. 

 A form of argument, described by logi- 

 cians, in which the conclusion actually 

 established is not the absolute and gene- 

 ral one in question, but relative and par- 

 ticular; viz., not that "such and such is 

 the fact," but that " this man is bound to 



