GLOSSARY. 63 



and west anticlinal axis. For a farther explanation, with a dia- 

 gram, see vol. iii. p. 293. 



ANTISEPTIC. Substances which prevent corruption in animal and 

 vegetable matter, as common salt does, are said to be antiseptic. 

 Etym.y avri) against, and aqiru, sepo, to putrefy. 



ARENACEOUS. Sandy. Etym., Arena, sand. 



ARGILLACEOUS. Clayey, composed of clay. Etym., Argilla, clay. 



ARRAGONITE. A simple mineral, a variety of carbonate of lime, so 

 called from having been first found in Arragon, in Spain. 



AUGITE. A simple mineral of a dark green, or black colour, which 

 forms a constituent part of many varieties of volcanic rocks. 



AVALANCHES. Masses of snow which, being detached from great 

 heights in the Alps, acquire enormous bulk by fresh accumula- 

 tions as they descend ; and when they fall into the valleys below 

 often cause great destruction. They are also called lavanges, 

 and lavanches, in the dialects of Switzerland. 



BASALT. One of the most common varieties of the Trap-rocks. It 

 is a dark green or black stone, composed of augite and felspar, 

 very compact in texture, and of considerable hardness, often 

 found in regular pillars of three or more sides, called basaltic 

 columns. Very remarkable examples of this kind of rock are 

 seen at the Giant's Causeway, in Ireland, and at Fingal's Cave, 

 in the island of Staffa, one of the Hebrides. The term is used by 

 Pliny, and is said to come from basal, an ./Ethiopian word sig- 

 nifying iron, not an improbable derivation, inasmuch as the rock 

 often contains much iron, and as many of the figures of tha 

 Egyptian temples are formed of basalt. 



' BASIN' of Paris, ' BASIN' of London. Deposits lying in a great 

 hollow or trough surrounded by low hills or high land, some- 

 times used in geology almost synonymously with ' formation/ 



BELEMNITE. An extinct genus of the order of molluscous animals 

 called Cephalopoda, that inhabited a long, straight, and cham- 

 bered conical shell. Etym., fit\tiivov, belemnon, a dart. 



BITUMEN. Mineral pitch, of which the tar-like substance which is 

 often seen to ooze out of the Newcastle coal when on the fire, 

 and which makes it cake, is a good example. Etym., Bitumen, 

 pitch. 



BITUMINOUS SHALE. An argillaceous shale, much impregnated with 

 bitumen, which is very common in the coal measures. 



BLENDE. A metallic ore, a compound of the metal zinc with sul- 

 phur. It is often found in brown shining crystals, hence its 

 name among the German miners, from the word blenden, tQ 

 dazzle. 



