BLA 



their dye, than other bodies are by the 

 galls and alum which suffice for them. 

 The inflammability of black bodies, and 

 their disposition to acquire heat, beyond 

 those of other colours, are easily evinced. 

 Some appeal to the experiment of a 

 white and black glove worn in the same 

 sun ; the consequence will be, a very 

 sensibly greater degree of heat in the 

 one hand than the other. Others allege 

 the phenomena of burning-glasses, by 

 which black bodies are always found to 

 kindle soonest ; thus, a burning-glass, too 

 weak to have any visible effect at all up- 

 on white paper, will readily kindle the 

 same paper rubbed over with ink. 



Dr. Watson, the present Bishop of 

 LandafF, covered the bulb of a thermo- 

 meter with a black coating of India ink, 

 in consequence of which the mercury 

 rose ten degrees. Phil. Trans, vol. Ixiii. 

 Black clothes heat more, and dry sooner 

 in the sun, than white clothes. Black is 

 therefore a bad colour for clothes in hot 

 climates : but a fit colour for the linings 

 of ladies' summer hats. 



BLACK act, in law, so called from the 

 devastations committed in Hampshire by 

 persons in disguise, or with their faces 

 blacked ; to prevent which, it is enacted 

 by 31 George II. c. 42, that persons hunt- 

 ing, armed and disguised, and killing or 

 stealing deer, or robbing warrens, &c. or 

 setting fire to any house, barn, or wood, 

 or shooting at any person, or sending 

 anonymous letters, or letters signed with 

 a fictitious name, demanding money, &c. 

 or rescuing such offenders, are guilty of 

 felony without benefit of clergy. 



BLACK, bone, is made with the bones 

 of oxen, cows, Sec. and is used in paint- 

 ing ; but is not so much esteemed as 

 ivory -black. 



BLACK, currier's, a black made with 

 gall-nutts, sour beer, and old iron, term- 

 ed the first black. The second black, 

 which gives the gloss of the leather, is 

 composed of gall-nuts, copperas, and gum- 

 arabic. 



BLACK earth, a sort of coals found in 

 the ground, which the painters and lim- 

 ners use to paint in fresco, after it has 

 been well ground. 



There is also a black made with gall- 

 nuts, copperas, or vitriol, such as com- 

 mon ink. And a black made with silver 

 and lead, which serves to fill up the cavi- 

 ties of engraved things. 



BLACK, ivory, otherwise called velvet- 

 black, is burnt ivory, which becoming 

 quite black, and being reduced to thin 

 plates, is ground in water, and made into 



troches, to be used by painters, and by 

 jewellers, who set precious stones to 

 blacken the ground of the collets, and 

 give the diamonds a teint or foil. In or- 

 der to be good, it ought to be tender, 

 friable, and thoroughly ground. 



BLACK, lamp, the sooty smoke of rosin. 

 There is some in powder and some in 

 lumps, and is mostly brought from Swe- 

 den and Norway. It is used on various 

 occasions, particularly for making the 

 printer's ink, for which purpose it is mix. 

 ed with oil of walnuts, or linseed, and 

 turpentine, all boiled together. 



BT.ACK lead has long been known under 

 the name of plumbagx); it is however 

 properly denominated in the modern che- 

 mistry, according to its component parts, 

 a carburet of iron, it being compounded 

 of 90 parts of carbon and 1U iron. See 

 Inox, where its properties will be des- 

 cribed. 



Black-lead is found in different coun- 

 tries, but the very best, and the fittest 

 for making pencils, is found at Burrow- 

 dale in Cumberland, where it is obtained 

 in such plenty, that not only the whole 

 Island of Great Britain, but the Conti- 

 nent of Europe, may be said to be sup- 

 plied from thence. Beside the appli- 

 cation of this substance to the manufac- 

 ture of pencils, it is made into retorts 

 that will endure almost the strongest 

 heat. The powder of black-lead is used 

 in covering the straps for razors, and 

 with it stoves, &c. are preserved from 

 rust. 



BLACK rod, gentleman usher of, in Bri- 

 tish customs, is chief gentleman to the 

 King. He has also the keeping of the 

 chapter-house door, when a chapter of 

 the Order of the Garter is sitting ; and 

 in time of parliament attends on the 

 House of Peers. 



BLACKBURNIA, in botany, so called 

 in honour of John Blackburne, Esq. and 

 his daughter Anna, of Orford in Lanca- 

 shire : a genus of the Tetrandria Mono- 

 gynia class and order. Essential charac- 

 ter : calyx four-toothed ; petals four, elip- 

 tic; anthers heart-shaped; germ conic; 

 stigma simple ; pericarp, berry, with a 

 single seed. There is but one species, 

 viz. bipinnata, has the leaves alternate ; 

 abruptly pinnate, with two or three pairs 

 of leaflets, which are opposite, quite en- 

 tire, and very smooth ; panicles axillary, 

 smaller. It is in habit not unlike ptelea 

 trifoliata, and whether it ought to be se- 

 parated from that genus cannot be deter- 

 mined, till we are better acquainted with 

 the fruit. It is a native of Norfolk Island,, 



