B L A 



[ 56] 



BOG 



11-35, oxide of iron, 2'75, carbon 

 11, water 7.5. 



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 com- 

 pound of carbon, with a small 

 portion of iron, and some earthy 

 matters. It is of a dark steel-grey 

 colour, inclining to iron-black ; it 

 occurs regularly crystallised; in 

 granular concretions ; massive and 

 disseminated ; it has a greasy feel, 

 and blackens the fingers, or any 

 other substance to which it is 

 applied ; it is infusible ; and burns 

 with much difficulty. According 

 to Yauquelin its constituent parts 

 are carbon 92., iron 8. ; 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 

 combustion, converted nearly the 

 whole into carbonic 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 manu- 

 facture into black-lead pencils. It 

 is found in the primary, transition, 

 and secondary rocks. Anthracite 

 resembles and appears to pass into 

 plumbago, or black-lead ; common 

 coal, also, according to Bakewell, 

 sometimes graduates into plumbago. 



BLACK- WADD. An ore of manganese, 

 used as a drying ingredient in 

 paints. 



BLASTOIDE'A. An extinct order of 

 the class Echinodermata. The 

 genera, which are all extinct, are 

 Pentremites, Eleacrinus, Codonas- 

 ter, Zygocrinus, and Phyllocrinus. 



BLA'TTA. (llatta, Lat.) The cock- 

 roach, placed by Linnseus in the 



second order, Hemiptera, of the 

 seventh class, Insecta. 



BLENDE. (from llenden, Germ, to 

 dazzle, or blind.) Sulphuret of 

 zinc ; a metallic ore whose con- 

 stituent parts are zinc, iron, sul- 

 phur, and a trace of quartz. Blende 

 is called by the English miners 

 black-jack; it occurs in the lead 

 mines. The primitive form of its 

 crystals is a rhomboidal dodecahe- 

 dron ; there are several varieties 

 known, as brown blende, yellow 

 blende, black blende. 



BLOOD-STONE. (See Heliotrope.) He- 

 matites ; a variety of agate to which 

 the name bloodstone has been 

 applied from some absurd notion of 

 its efficacy in restraining hemor- 

 rhage. 



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 orna- 

 mental figures, being capable of 

 being turned by the lathe. Bake- 

 well, in describing the blue-John, 

 or fluor spar mine near Castleton, 

 in Derbyshire, observes, " the 

 crystallizations and mineral incrus- 

 tations 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 descrip- 

 tions of the grotto of Antiparos 

 translated into the simple language 

 of truth, I am inclined to believe it 

 would be found inferior in magni- 

 ficence, and splendour of mineral 

 decoration, to the natural caverns 

 of the fluor mine." 



BLUE VITKOIL. Sulphate of copper. 



BLUFE. Any high head-land, or 

 bank, presenting a precipitous front. 



BOG-IEON-ORE. ( Iron ore peculiar to 



BOG-OEE. ( boggy land. Sir 



C. Lyell observes, " at the bottom 

 of peat mosses there is sometimes 

 found a cake, or pan, of oxide of 

 iron, and the frequency of bog-iron 



