354 \? roc - B.N.F.C., 



at Shane's Castle, in 1837, by Dr. Scouler, who supposed it to be 

 pitchstone ; at a later date Portlock refers to it as obsidian ; the 

 Geological Survey call it by the same term. Mr. E. T. Hardman, 

 F.C.S., of the Geological Survey, however, determined its real na- 

 ture by chemical and microscopic examination. The result of his 

 researches proved the black mineral to be a remarkably distinct 

 new mineral, belonging to the chlorito-ferruginous group. He 

 named it Hullite, after Professor Hull, F.R.S., a gentleman well 

 deserving the compliment for his zeal in working out the sequence 

 of the volcanic rocks of his native County Antrim. 



Before describing in detail the various minerals and their mode 

 of occurrence, Mr. Gault briefly noticed these volcanic necks, as 

 they are very seldom visible. It is only when denudation has re- 

 moved all the covering from the top, or cut for us a section along 

 some hillside or seashore, that we find oval or circular masses of 

 hard crystalline basaltic rock, very often prismatic in structure, 

 standing out from or elevated above the surrounding strata. These 

 bosses of basalt rock are the plugs of the volcanic orifices, and 

 differ in form and other peculiarities from the longitudinal dykes 

 that are so numerous in this district. They are not the original 

 cones from which the lava and ashes were ejected, for these would 

 be higher than the deposited material, and in this district have been 

 entirely obliterated by the severe denudation they suffered during 

 the Pliocene and glacial epochs. This is proven by the fact of the 

 removal of all the beds of iron ore and sheets of upper basalt, in 

 thickness amounting to about 500 feet, that covered the whole of 

 the County Antrim south of the great downthrow fault of the Six- 

 milewater valley. Only a few patches of these important deposits 

 now remain on some of the higher elevations to attest their former 

 wide extension. The Pliocene clays of Lough Neagh have been 

 largely made up with the material denuded from the South Antrim 

 plateaux. Some of the masses of dolerite and other basaltic rocks 

 in the North Antrim district said to be volcanic necks, are very 



