DOMAIN XII. VOLCANIC. 



the lavas*. But Ferrara seems to have decided 

 this inquiry. 



Porous basaltin, with olivine, from Etna. 



The same, with leucite, from Vesuvius. 



The same, with augite, the pyroxene of Haiiy ; 

 which contains about 15 of iron, and seems a 

 mere modification of siderite. 



Micronome 1. Grey compact lava. 



All lavas, as already mentioned, with a few tri- 

 fling exceptions of mere curiosity, may be classed 

 in two divisions : those with a base of siderite, 

 and those with a base of felsite. The grey lavas 



* P. 52. Chrysolite, or olivine, is common in native iron, and 

 in lava, ib. 217. Gallitzin (Rec. des Noms, Brunsw. 1801, 4to.) 

 mentions an iron ore articulated like basalt, mine de fer en prismes 

 articuUs, comme le lasalte. Brochant has a red hematite of iron in 

 prisms, from the Fichtelberg near Bareuth. 



The pretended basaltin of Wales, observed by Strange and others, 

 at Cader Idris, is, according to recent and more accurate observers, 

 a coarse grunstein or basalton, in rude oblong fragments occasioned 

 by fissures. Appearances more volcanic may be traced in the north 

 of Ireland ; where the red earth resembles puzzolana; the krag of 

 Kirwan, found near Belfast, is very porous ; and the mullen seems to 

 some an ash-grey lava with hornblende. Deluc, Geol. 273, ex- 

 presses his belief in the extinct volcanoes of Germany, and says that 

 sections of lava may be observed turned to a central point, and 

 forming circles of hills around an empty space, the focus having 

 sunk and disappeared. He calls these volcanic crowns; and the 

 centre is often a lake. 



