310 Sciriififfr Proceedings, Royal Dublin Society. 



to have supplied the material for the iron ore now found in the 

 underlying or older beds. Thus the iron ores in the Carboniferous 

 limestone may have permeated downward during the formation of 

 the Coal-measures ; the Silurian iron ores during the formation of 

 the Carboniferous rocks, &e., &c. Such a theory, however, will not 

 account for all of the iron ore accumulations, as will appear from 

 the brief descriptions given in the second part of some of the Irish 

 lodes and other accumulations. 



Paet II. 



In the first part of this Paper we drew attention to the iron 

 ores in the surface accumulations, and their probable mode of for- 

 mation ; while in this it is proposed to refer more specially to the 

 lodes, and such like, in the older rocks, accompanied with sugges- 

 tions as to the possible sources from whence the iron may have 

 come, beginning with the Tertiary Iron Ore Measures of the 

 county of Antrim. 



Antrim Iron Mines. 

 The Tertiary dolerites of the counties of Derry and Antrim, con- 

 tain interbedded Iron Ore Measures. These appear to have been 

 lacustrine deposits, which accumulated in shallow lakes or ponds of 

 water, in hollows on ancient surfaces of the lava sheets, to be sub- 

 sequently covered up by newer sheets of the dolerite. When fully 

 developed the members of these measures are : — 



1. Lithomarge, or laterite, with inliers of bole 



2. Ochreous rock (Pavement). 



3. Bole, or alumnious ore [second ore). 



4. Pisolitic, or pebble ore {first ore). 

 6. Steatitic rock (Brushing). 



6. Steatitic clay (Holing). 



7. Alumite (or alum clay). 



8. Lignite. 



The lignite and alumite' occur only near the margins of the 

 different basins, wholly, or in part, replacing the iron ores (3 and 4). 



^ Alumite is somewliat similar to the Frencli clay called Bauxite, and is often so 

 named. 



