158 Scientific Proceedings, Royal Dublin Society. 



thirty inches due to a cavity or " rise " in the roof (a roll or 

 " gurry " of the miners) ; also an irregular wavy or undulating- 

 structure in the roof may thin and thicken the seam alternately. 

 Small cavities or rugs in the roof are usually filled or lined with 

 beautiful crystals of aragonite, sometimes stained red but usually 

 colourless. 



A steatitic clay, like No. 5 in the general section (page 155), is 

 sometimes found separating two beds of pisolitic ore, the upper 

 bed being usually of a red colour ; but I have only found this in 

 disturbed areas. Very often the pisolitic ore is found resting 

 unconformably on the pavement, the bole and pavement having 

 evidently been worn away in places before the ore was deposited 

 (see Plate XVIII.) ; also it is not uncommon to find angular and 

 rounded pieces of aluminous ore and pavement in the pisolitic 

 ore seam, thus giving it a brecciated appearance. In approaching 

 a place where the pisolitic structure of the ore is not well 

 developed and where the ore appears to be indurated by some 

 cause, we usually find a great display of acicular crystals of 

 aragonite on the roof with veins and partings in the ore, which 

 sometimes cement it to the roof; hence a display of crystals on 

 the roof is regarded by some as a sign of poverty ; similarly as a 

 display of spar crystals in a standing vein indicates poverty of 

 mineral matter in the percolating fluids when the vein was being- 

 filled. 



Sometimes the pisolitic ore is absent and the second ore rises 

 to the roof; at other times both the ores, thus causing the pave- 

 ment and the roof to join together; this cutting out of the ores 

 is generally caused by the roof dipping down on the pavement. 

 (Plate XVIII.) 



The pisolitic ores are more or less magnetic, some being mag- 

 natite. In regard to their colours, the red are only slightly or 

 not at all magnetic ; while the brown are also, they may graduate 

 into a black true m?ignatite ; the latter contains 8 to 15 per cent, 

 titanic acid, and is very rich in iron. I have frequently found 

 the pisolites of magnetic ore to be polaric, their elongated axis or 

 poles being horizontal in the seam, and apparently conformable 

 with the present magnetic meridian. 



Lignite and bauxite are found to occur in connexion with the 

 iron ore measures in various parts of the county Antrim, and 



