B I T 



C 32 ] 



BOG 



much impregnated with bitumen, which 

 is very common in the coal measures. 

 LyelL 



BITU'MINOUS SPRINGS. We are informed 

 by Mr. Lyell that springs impregnated 

 with petroleum, and the various minerals 

 allied to it, are very numerous, and are, 

 in many cases, undoubtedly connected 

 with subterranean fires. The most pow- 

 erful yet known, are those on the Irawadi, 

 in the Burman empire, which, from one 

 locality, are said to yield 400,000 hogs- 

 heads of petrdleum annually. 



BI'VALVE. (bivalvis, Lat. bivalve, Fr.) 

 An animal having two valves, shells, or 

 shutters, as the oyster, muscle, &c. 



BI'VALVE. "^ Consisting of two valves 



BIVA'LVULAR. > or divisions ; having two 



BIVA'LVOUS. J valves, or shells. 



BLACK CHALK. A clay of a bluish black 

 colour, extremely soft, a quality which it 

 owes to the presence of about twelve per 

 cent, of carbon. That most esteemed is 

 found in Italy and Germany, and takes its 

 name from those countries respectively. 



BLACK-JACK. A name given by miners to 

 a sulphuret of zinc. See Blende. 



BLACK-LEAD. The substance about to be 

 described has been thus named from its 

 leaden appearance, or general resemblance 

 to lead, but it does not in fact contain a 

 single particle of lead in its composition. 

 It is the same as plumbago and graphite. 

 Black-lead is a compound of carbon, with 

 a small portion of iron, and some earthy 

 matters. It is of a dark steel-grey co- 

 lour, inclining to iron-black ; it occurs 

 regularly crystallised ; in granular con- 

 cretions ; massive and disseminated ; 

 it has a greasy feel, and blackens the fin- 

 gers, or any other substance to which it is 

 applied ; it is infusible, and burns with 

 much difficulty. According to Vauquelin 

 its constituent parts are carbon 92*0, 

 iron 8'0 ; but according to Allen and 

 Others, it contains only five parts per 

 centum of iron. Its nature was first in- 

 vestigated by Scheele, who, by combus- 

 tion, converted nearly the whole into car- 

 bonic acid gas, the residuum being oxide 

 of iron. Black-lead, or carburet of iron, 

 is used for many domestic purposes, but 

 its principal use is in its manufacture into 

 black-lead pencils. It is found in the 

 primitive, transition, and secondary rocks. 

 Anthracite resembles and appears to pass 

 into plumbago, or black-lead ; common 

 coal, also, according to Bakewell, some- 

 times graduates into plumbago. 



BLACK-WADD. An ore of manganese, used 

 as a drying ingredient in paints. 



BLA'TTA. (blatta, Lat.) The cockroach, 

 placed by Linnseus in the second order, 

 Hemiptera, of the seventh class, In- 

 sects. 



BLENDE, (from blenden, Germ, to dazzle, 

 or blind.) Sulphuret of zinc ; a metallic 

 ore whose constituent parts are zinc, iron, 

 sulphur, and a trace of quartz- Blende 

 is called by the English miners black- 

 jack. The primitive form of its crystals 

 is a rhomboidal dodecahedron ; there are 

 several varieties known, as -brown blende, 

 yellow blende, black blende. 

 j BLOOD-STONE. Hematites ; a variety of 

 agate to which the name blood-stone 

 has been applied from some absurd 

 notion of its efficacy in restraining he- 

 morrhage. 



BLUE-JOHN. A name given by the miners 

 to fluor spar ;- called also Derbyshire 

 spar, in which county it occurs in great 

 abundance. It is manufactured into 

 vases and ornamental figures, being ca- 

 pable of being turned by the lathe. Bake- 

 well, in describing the blue-John, or 

 fluor spar mine near Castleton, in Der- 

 byshire, observes, " the crystallisations 

 and mineral incrustations on the roof and 

 sides of the natural caverns which are 

 passed through in this mine, far exceed 

 in beauty those of any other cavern in 

 England ; and were the descriptions of 

 the grotto of Antiparos translated into 

 the simple language of truth, I am in- 

 clined to believe it would be found in- 

 ferior in magnificence and splendour of 

 mineral decoration, to the natural caverns 

 of the fluor mine. 



BLUE VITRIOL. Sulphate of copper. 



BLUFF. Any high head-land, or bank, 

 presenting a precipitous front. 



BOG. (log, Irish, soft.) A kind of mo- 

 rass, too soft to bear a man's weight, and 

 partly composed of decayed vegetable 

 matter. 



BOG-IRON-ORE. } Iron ore peculiar to bog- 



BOG-ORE. S gyland. Mr. Lyell ob- 



serves, " at the bottom of peat mosses 

 there is sometimes found a cake, or pan, 

 of oxide of iron, and the frequency of 

 bog-iron ore is familiar to the mineral- 

 ogist. From what source the iron is de- 

 rived is by no means obvious, since we 

 cannot in all cases suppose that it has 

 been precipitated from the waters of mi- 

 neral springs. It has been suggested that 

 iron, being soluble in acids, may be dif- 

 fused through the whole mass of vege- 

 tables, when they decay in a bog, and 

 may, by its superior gravity, sink to the 

 bottom, and be there precipitated so as to 

 form bog-iron ore. Dr. Mantell ob- 

 serves, " the formation of what is termed 

 bog-iron ore, found in marshes and peat 

 bogs, is supposed to have been derived 

 from the decomposition of rocks over 

 which water has flowed ; but the observ- 

 ations of Ehrenbergh, seem to indicate 

 a different origin." 



