BAR 



[48] 



B A S 



BABE LIMESTONE. An argillaceous, 

 concretionary limestone, nodular 

 and interstratified with beds of 

 shale. A rock of the Upper Silu- 

 rian series. 



BAEYSTKO'NTIANITE. (from fiapvs, 

 heavy, and strontian.) This min- 

 eral has also obtained the name of 

 Strom nite, from its being found at 

 Stromness, in the island of Pomona. 

 Its principal constituent is carbon- 

 ate of strontia, of which it contains 

 nearly 70 per cent., combined with 

 sulphate of baryta and a small pro- 

 portion of carbonate of lime and 

 oxide of iron. It occurs massive, 

 of a greyish colour externally, and 

 of a yellowish white internally. 

 BAEY'TA. \ from fiapvs, heavy, Gr.) 

 BA'EYTE. Barytes has been also 



BARY'TES. ) called ponderous spar, 

 heavy spar, and barote. The first 

 account of the properties, &c. of 

 barytes, was published by Scheele 

 in his dissertation on Manganese. 

 It has obtained its name from its 

 great specific gravity, which is 

 about 4, being the heaviest of all 

 the known earths. It was called 

 barote by Morveau, and barytes by 

 Kirwan. Barytes converts vege- 

 table blues to green. When ex- 

 posed to the atmosphere it attracts 

 moisture, and when water is poured 

 upon it the same appearances pre- 

 sent themselves as in the slaking 

 of lime, with the evolution of great 

 heat, the process being more rapid, 

 and the eyolution of heat greater. 

 Barytes is found in two natural 

 combinations only, with the sul- 

 phuric and carbonic acids, forming 

 sulphate and carbonate of barytes. 

 The primitive crystal of sulphate 

 of barytes is, according to Haiiy, a 

 right prism with rhombic bases; 

 the measurements by the reflecting 

 gonionometer, according to Prof. 

 Phillips, are 10T42' on the one 

 angle,and 78ir on the other. It 

 is a violent poison. Nearly all the 

 compounds of barytes are poisonous, 



the best antidotes being dilute sul- 

 phuric acid, or sulphate of soda in 

 solution. 



BAEY'TIC. Containing barytes; re- 

 sembling barytes ; having the pro- 

 perties of barytes. 



BA'SALT. (Said to be derived from 

 an Ethiopian word, basal, signify- 

 ing iron.) A variety of trap-rock 

 of a dark green iron grey or brown- 

 ish black colour, composed of 

 augite and felspar with some iron 

 and olivine, the predominant min- 

 eral being felspar. Sir H. de la 

 Beche says that basalt is supposed 

 to be essentially composed of 

 augite, and titaniferous iron. Ber- 

 thier says " mais c'est surtout dans 

 les roches volcaniques que le titane 

 abonde ; il y est toujours combine 

 avec le fer et le manganese." 



The following are some of the 

 usual characters of the basaltic 

 rocks of this country; considerable 

 tenacity and hardness, a sharp, and 

 sometimes conchoidal fracture; a 

 granular aspect, often reflecting 

 light from a number of brilliant 

 spots or striae, some of which seem 

 to be felspar, others hornblende or 

 augite ; very subject to superficial 

 decomposition, in which case the 

 colour passes to a rusty brown, 

 often mingled with spots of green, 

 arising apparently from grains of 

 hornblende. Basaltic rocks are 

 fusible at a low degree of heat, and 

 attract the needle strongly. Sp. 

 gr. of the basalt of Staffordshire is 

 2.86. 



Basalt occurs, sometimes, in 

 veins or dykes, which traverse 

 rocks of all ages, filling up fissures 

 or crevices, and at others, in layers 

 spread over the surface of the 

 strata, or interposed between them. 

 Many modern lavas differ so little 

 from basalt, that it is unnecessary 

 to adduce proof of the volcanic 

 nature of this rock. It often 

 occurs in the form of regular pillars, 

 or columns, clustered together ; or, 



