B A S 



net ; the " Envir0n3.de Groningue" and the " Environs 

 de Gucldies," from Ruyfdaal. Striitt. 



Bas, John Le, a furgcon and accoucheur of confiderable 

 eminence, born at Orleans, was admitted at the academy of 

 furgeons of Pario, in 1756, wlierc he rtfided. Called upon 

 in 1764 to give an opinion as to the legitimacy of a child born 

 ten months and fcventeen days after the death of the fup- 

 pofed father, he decided in its favonr ; but the caufe being 

 referred to another comt, the afliilance and opinion of Bou- 

 vart, Ant. Lewis, Petit, and feveral ether phyficians and fur- 

 geons, were demanded, v.^ho unaiiimoufly declared againfl the 

 decifion of Le Bas. This gave rife to a furious literary dif- 

 pute, in the courle of which feveral pamphlets were written 

 on each lidc. Le Bas defended the part he had taken, by 

 the authority of Arillotle and Pliny, fupported by Schen- 

 kius and other modern recordei"S of extraordinary events, 

 as well as by the decifions of the courts of law in various 

 parts of Europe, which had been fometimes given in favour 

 of births protratled to even more than twelve months, which 

 Le Bas thinks might, and, he had no doubt, had happened. 

 Bouvart and Louis, on the contrary, contending againll the 

 authority of thefe pretended cafes of protrafted gellation 

 brought by their antagonill, which they do not admit to 

 have been completely proved in any one inllance, fix the 

 time of parturition in women to nine calendar months from 

 the time of conception ; allowing it may be extended be- 

 yond that time ten or twenty days, and denying that in any 

 one well-authenticated cafe, proof had been produced of a 

 woman's being delivered of a living child later than that 

 period. This opinion is now, we believe, univerfally efta- 

 blifhed. The fi;llowing are the titles of the books written 

 by Le Bas on the fubjeft : " Queftion important : Peut on 

 deter^niner le tems dc I'accoiichement," Paris 1764, 8vo. 

 " Nouvelles obfervations fur l.s nailTances tardives," ijd^, 

 8vo. ; written in anfwer to Louis, who had confuted his argu- 

 ments, and denied the authenticity of the cafes brought in 

 fupport of them. " Lettre a M. Bouvart, au fujet de fa 

 derniere confultation," 1765, 8vo. Bouvart had taken the 

 fame fide with Louis. " Repliq le a un ouvrage de 

 M. Bouvart," 1767, 8vo. This is written with much acri- 

 mony ; the lad refourcc, when defending a bad caufe. Hal- 

 Itr. Bib. Chirurg. 



Bas, in Geography, a fmall idand in the Englifh chan- 

 nel, near the coall of France, v.'hich has a fort to defend the 

 road, and contains about fifty inhabitants. N. lat. 48° 50'. 

 W. long. 4°. 



Bas, Point de, is the fonthcrn cape of a bay which runs 

 in eadward from Quiberon bay on the foulh of Vilacre river, 

 on the well coaft ot France. 



Bas en Bajfcl, a town of France, in the department of 

 the Upper Loire, and chief place of a canton in the diftnd 

 of Moniftrol ; one league north weft of Moniftrol. 



Bas Relief. See Basso relievo. 



BASAAL, in Botany, the name of an Indian tree, grow- 

 ing about Cochin. Ray's Hill. 



BASAG, in indent Geography, an idand of the Indian 

 ocean, near Arabia Felix, according to Pliny. 



BASALT, artificial, or black porcelain, a compofition 

 having nearly the fame properties with the natural bafalt, in- 

 vented by Melfrs. Wedgwood and Bentley, and applied to 

 various purpofes in their manufaftures. 



Basalt, in Mineralogy. Argilla bafaltes, Werner ; fcu- 

 rate trap of Kirwan. ^ 



The colour of this mineral is generally greyifh black, more 



rarely bluilh or brownilh black ; its furface is ufually rcddifli 



brown, from a partial decompofition. It is found in large 



maffes, compofing entire ini'ulated mountaina of a fomewhat 



2 



BAS 



conical form. Of itfelf it is deftitute of luftre, but not un- 

 frequently contains ihining particles of olivin or baialtic horn- 

 blende. Its fraclure is uneven, paffing into fine fplintery, 

 fometimes approaching to the even or flat conchoidal. It 

 flies, when broken, into indeterminate rather iharp-edged 

 fragments. 



The moft ufual form of bafalt is that of columns, ftraight 

 or curved, perpendicular or inchncd, from three inches to 

 three feet in diameter. Thefe pillars are divided either by 

 fimple fecHons at right angles to their axes, or by articula- 

 tions formed by the convex end of one piece infcrted into 

 the concave extremity of the adjoining one. Tlie forms of 

 the columns are pentangular, hexangular, odlangular, rarely 

 triangular or quadrangular. Balalt alfo fometimea occurs in 

 tables, or in globular or elliptical concentric maffe;, called 

 by the French bafalte en bouks. 



It gives a clear arti-grey llreak, is almoft hard enough to 

 give fire v.'ith fl:eel, and is very dif&cidtly broken. It is ge- 

 nerally opaque, though fometimes flightly tranflucid on the 

 edges. It is remarkably fonorous when ftruck with the 

 hammer. Sp.gr. according to Bergman, 3; Briffon, 2.864. 

 It is fometimes magnetic. 



Before the blowpipe, bafalt fufes without addition into a 

 black opaque glafs, attraftable by the magnet. When 

 heated in a charcoal crucible, according to Klaproth, it fufes 

 into an afii-grey mafs, of a dull earthy frafture, and mi- 

 nutely fpongy texture, overlaid with grains of iron : it lofes 

 in this procels 9 per cent, of its weight. In a clay crucible, 

 it fufes into a denfe glafs, opaque in mafs, but tranfparent, 

 and of a clove-brown colour, in thin fphnters. 



Its conllicucnt parts, according to Bergman, are ; 



The geological charadlcrs of bafalt, and the various con- 

 troverfies with regard to its origin, and that of the other 

 Rods of Secondary Trapformation, will be treated of 

 at large in their proper place. It will be fufficient to men- 

 tion here, that bafalt belongs to the Itratined mountains, 

 and that it very rarely contains any petriiaAions. When in 

 mafs, it never indoles any metallic veins ; and wlien it occurs 

 in the form of dykes, in coal Itrata or metalliferous rocks, it 

 produces a total ieparation of the ore or coal on each fide of 

 the dyke. 



It is feldom if ever quite pure, being generally mixed with 

 bafaltic hornblende, common hornblende, and olivin ; more 

 rarely with zeolite, felfpar, quartz, fchorl, and calcareous 

 fpar. Mica is fometimes found on its furface, though very 

 feldom penetrating its fubllance. When mingled with thefe 

 in confiderable proportion, it is eafily decompolable into a 

 remarkably fertile clayey loam. 



The north-eaft coaft of Ireland prefents the moft perfeft 

 and magnificent ranges of bafaltic columns in the world : 

 the celebrated Giants' caufeway is an affemblage of 

 many thoufand articulated pillars projeding into the fea, at 

 the foot of a lofty bafaltic promontory, exhibiting a poly- 

 gonal pavement fomewhat refembling a folid honeycomb. 

 The promontory at Fairhead is a vail colonade of upright 

 bafaltic pillars, the fliafts of which arc 250 feet in length. 

 Scotland alfo contains many beautiful fpecimens of columnar 

 bafalt : the little ifland of Staffa in particular almoft entirely 

 confills of bafaltic pillars, both vertical and bending. The 

 central diftnd of Auvergne in France, and the northern 



parts 



