Page:The New International Encyclopædia 1st ed. v. 02.djvu/653

BASILIDES. sics, ed. Lightfoot (Ijondmi, 1875) ; Hurt, "Basilides," iu Smith and Wace, Dictionary of Christian Biography (Loudon, 1887); Sehaff, Bisloru of the Christian Church, II., 466-472 (Now York, ISOl). Sec further, under Gnosti- cism.

BASILIO DA GAMA, ba-ae'Ie-o da ga'ma, Jo.sii. See Gaiia, Jost Basii.io da.

BAS'ILIS'CUS (Gk. BairMa-Kos, Sasiliskos). Kiiipei'or of the East from 47U to 477. He was brother-iu-law of the Emperor Leo I. In 468 he liad led the great African expedition against Geiiserie, the Vandal, which ended disastrously. His reign was uneventful. He was deposed by Zcno in 477, and died the following year.

BASILISK, hriz'i-lisk (Gk. /SacriXiirKos, basi- lislcos, diniin. of ^acriXeus, basileus, king, same as Lat. regulus, little king. So named, ac- cording to Isidor, because it was the king of ser])ents, but perhaps by reason of the crest on its head). A fabulous creature, resembling a serpent, and supposed by the ancients to inhabit the Libyan Desert. It was described as being of a yellowish color, with spots of white, and as having a pointed head, whereon stood one or more prominences, also white, resembling a diadem. Its breath was considered to be espe- cially poisonous, and its glance fatal. The word h'jsilisk is now applied to a sort of lizard, having an erectile crest along the middle of the back and tail, and a dilatable pouch on the head.

BASIL'IUS VAL'ENTI'NUS. See Valen- tin us, Basiuus.

BA'SIN (OF. bacin, from Lat. bachinus, from hacca, water-vessel). In geology and hydro- graphy, a depression of the earth's surface, or of the strata constituting the crust of the earth, also the drainage area of a river system. Basins originate in several ways, and may lie grouped under two general heads : those formed by erustal movements and those due to erosion. Most biisins are due in part to both agencies. Basins formed by movements of the earth's crust are apt to be of great extent according as they owe their origin to either localized or continental movements. The Mississippi Valley, previous to Tertiary time, was occupied by a shallow arm of the sea that covered the central portion of the North American continent. Elevation of the continent raised the district above sea-level and drained the marine waters from the land, and onigenie movements partially surrounded it with nunnitains, with the result that an extensive interior basin was formed, the larger part of which is now drained by a single river system, that of the Mississippi. Other porticms of the same basin are drained by the Saint I^awrence River and by the rivers that How into the Arctic Ocean. We have here an example of a geologic basin that contains several hj'drograjjhic basins. The inclosed basins of Utah, Nevada, Arizona, and Mexico have been formed by local move- ments, folding, and faulting of the crust, that have culminated in the elevation of mountains inclosing plains. The elevation of the moun- tains has cut these plains ofl' from the supply ot moisture-laden winds, and arid desert con- ditions have largely ensued. During a former more humid period in Pliocene time great lakes occupied many of these basins, but their waters have disappeared largely through evaporation and lack of supply by rains, and concentrates of alkali, salt, and gj'jjsum now cover large areas of their desert bottoms, while traces of their foi-mer shore lines are to be found far up on the mountain sides. See Lake Bonneville; Lake Lahontan ; Gkeat Salt Lake.

Another form of basin results when a section of the earth's crust subsides between two nearly parallel great faults or dislocations, to form what is known as a 'rift valley' (i, v.). The most striking basins of this kind are found in Western Asia and Eastern Africa. The largest basin in this region begins north of the Dead Sea. and ex- tends southward through the valleys of the Dead Sea, the river Jordan, and the Red Sea, whence the rift is continued in a southerly direction across Eritrea in Africa, to a point near Mount Kilimanjaro. This may be considered a continu- ous single depression or rift-valley basin, with a length of about .3.500 miles and a maximum width at the Red Sea of 200 miles. Another such depression extends westward of the Victoria Nyanza for nearly 1.500 miles in a general south- erly direction, and includes the valleys of the Albert Nyanza, Tanganyika, and Nyassa. ter- minating at the coast in the vicinity of the mouth of the Zambezi River. The amount of dis- placement of the bed of this latter rift has been enormous, the vertical throw of the faults having been at least 5000 feet in the vicinity of Lake Tanganyika. In volcanic regions basins lilled by lakes often occur in the craters of extinct vol- canoes. Crater Lake, in Oregon, is a good ex- ample.

In coal-mining regions the term basin is ap- plied to synclinal depressions of the coal-bearing strata that have been produced by the folding of the beds incident to their elevation into moun- tains. Such a stratigraphie basin in the crust of the earth is not usually co-extensive with a hydrographie basin on the surface, for the reason that synclinal depressions generally occupy ridges. The anticlinal upfolds have been worn away by weathering, and are now replaced by vallej's or hydrographie basins.

Basins formed by erosion are of two kinds, those formed bj' the work of rivers and those due to the wearing action of glacier ice. The former are the larger and more common, though the latter often constitute prominent features of the landscape of northern countries. The basin of a river, when considered hydrogra])hically, con- sists of the entire area drained by the main stream and its tributaries. This hydrographie basin may be in large part the result of oro- genic movements: but its present boundaries have been determined entirely bj' the cutting power of its streams, and accordingly a hydrographie basin may consist of one or more geologic basins. The Hudson River system furnishes a good example of such a complex basin. The Lower Hudson River, from New York City to Peekskill; the Up- per Hudson, from Peekskill to the Adirondacks; the Schroon River in the Adirondacks; the Mohawk River; the Schoharie, Esopus, and Cats- kill creeks, in the Catskill Mountains; and the Rondout in the Shawangunk Mountains all drain distinct geological basins, the divides between which have been cut down by the rivers, till now the entire region is included in a single hydro- graphie system.

Glacial basins have been formed by the eroding power of ice acting on the floor and sides of valleys already formed by some other means.