BIT 



BL A 



by 1000; nine, by 1001; ten, by 1010, 

 &c. 



BIO'GRAPHY (/3t'o?, life, -ipacph^ writ- 

 ing). That department of literature 

 which treats of the lives of individuals. 

 It is thus distinguished from history, 

 which treats of states and nations. 



BIRD'S-EYE VIEW. A mode of 

 prone perspective representation, by which 

 objects are shown, in nature or in paint- 

 ing, below the spectator, who can see 

 them only by looking down upon them. 

 The reverse of this is the supine per- 

 spective, termed di solto in su, employed 

 for ceiling-pieces, which the spectator 

 can view only by looking upwards. 



BIRDS' NESTS, ESCULENT. The 

 nests of the Hirundo esculenta, a species 

 of swallow peculiar to the Indian islands, 

 formed of a viscid substance, not unlike 

 isinglass. Nothing satisfactory is known 

 as to the formation of these eatable 

 nests. 



BI'SMUTH {wismuth, German). A 

 reddish-white metal, usually found in tin 

 mines. It occurs as an oxide, under the 

 name of bismuth ochre; as a sulphuret, 

 called bismuth glance; as a sulphuret 

 with copper, called copper bismuth ore; 

 and with copper and lead, called needle 

 ore. The subnitrate is known, in Phar- 

 macy, under the name of magistery of 

 bismuth. The sublimed oxide is known 

 by the name of flowers of bismuth ; the 

 chloride as the butter of bismuth. An 

 alloy of bismuth, lead, and tin, consti- 

 tutes Newton's fusible metal. 



BISSE'XTILE, or LEAP-YEAR. A 

 term adopted in the Julian calendar. 

 Julius Caesar, having ascertained that 

 the solar year consisted of 365^ days, 

 made the civil year 365 days, and added 

 a sixth at the end of four years, to com- 

 pensate for the quarter of a day dropped. 

 This fourth year, which contained 366 

 days, was termed bissextile, from its 

 doubling the 24th of February, or, ac- 

 cording to the Roman way of reckoning, 

 the sextilis, or sixth of the calends of 

 March {bissextus dies). This arrange- 

 ment was denominated the Julian Style, 

 or the Old Style, as distinguished from 

 the Crregorian or New Style. 



BISTRE. A brown pigment, made 

 from the roots of beech and other woods, 

 reduced to soot, and then boiled and 

 evaporated. 



BITTER PRINCIPLE. A general 

 term applied to an intensely bitter sub- 

 stance, procured by digesting nitric acid 

 on silk, indigo, &c. The bitter of Welter 

 53 



is the former name of picric or carbazotic 

 acid, formed by the action of nitric on 

 anilic or indigotic acid. 



BITTERN. The mother water, or un- 

 crystallizable residue left after muriate 

 of soda has been separated from sea-water 

 by crystallization. It owes its bitterness 

 to sulphate and muriate of magnesia. 

 It contains bromine. 



BI'TTERSPAR. Rhombspar. A crys- 

 talline mineral, bearing the same relation 

 to dolomite and magnesian limestone, 

 that calcareous spar does to common 

 limestone. 



BITU'MEN {iriTv^xa, iririK, pine). A 

 mineral pitch, supposed to be formed in 

 the earth by the decomposition of animal 

 and vegetable substances. In its most 

 fluid state it constitutes naphtha; when 

 of the consistence of oil, it becomes joe^ro- 

 leum ; at the next stage of induration it 

 becomes elastic bitumen; then maltha; 

 and so on until it becomes a compact 

 mass, and is then called asphaltum. 



BITU'MINOUS SHALE. An argil- 

 laceous shale, much impregnated with 

 bitumen, which gives it a dark brown or 

 blackish colour; its structure is slaty, 

 the streak brown and shining. 



BI'VALVE {bis, twice, valvce, folding- 

 doors). A shell which has two valves, 

 belonging to the order Dithyra. 



BLACK COMPOUNDS. 1. Black 

 lead, or plumbago, is a carburet of iron, 

 found in a pure state only at Borrowdale 

 in Cumberland. It derives its name from 

 its leaden appearance, for it does not 

 contain a particle of lead. 2. Black dye 

 is a compound of oxide of iron with gallic 

 acid and tannin. 3. Black flux is a mix- 

 ture of charcoal and carbonate of potash. 

 4. Black chalk is a mineral found in 

 primitive mountains, and sometimes near 

 coal formations. 5. Black jack is the 

 technical term for blende or mock lead, 

 an ore of zinc. 6. Black wadd is an ore 

 of manganese, called the black oxide, 

 and used as a drying ingredient in paints. 

 7. Black turpeth is the protoxide of mer- 

 cury, commonly called the gray, ash, or 

 black oxide. 8. Lamp black is a species 

 of charcoal procured by burning resinous 

 substances in a furnace. 9. Spanish black 

 is also a charcoal made of burnt cork, 

 andfirstused by the Spaniards. 10. Black 

 salts, is the name given in America to 

 wood-ashes, after they have been lixi- 

 viated, and the solution evaporated, until 

 the mass has become black. 



BLADDER GREEN. A green pig- 

 ment, prepared from the ripe berries of 

 D3 



