314 Scientific Proceedings, Iloi^'iil JJublin Society. 



county Wicklow (hereafter to be described), as it shrunk away from 

 the underlying sulphur lode, forming a horizontal fissure, which 

 in part remained open (if we except the water that was in it), 

 while in part it was occupied by a " gossan lode." As the latter 

 contained minerals not a trace of which has been found in the 

 normal lode, they suggest that the gossan lode was filled from above 

 by foreign minerals in solution : this " gossan lode," therefore, 

 seems to have been filled somewhat similarly to the horizontal iron 

 lodes of the county of Antrim. In the latter case the boggy water has 

 leached the iron out of the dolerite ; while, as mentioned by Argall, 

 in places on the surface, where the bog water comes in contact with 

 the dolerite, beds of bog iron ore are forming. It is worthy of note 

 that where the " through dykes" cut the pisolitic, the latter is often 

 changed into magnetite. 



Dysert and Dunamase, Queen's County, v^ith Kilcolman 



AND ShANAGOLDEN, CoUNTY OF LiMERICK. 



At these Queen's County and Limerick localities there are old 

 mines and veins of limonite mixed with hematite. At Dysert 

 there are the remains of old workings that cannot be properly 

 examined. In one place the ore seems to be in a mass of " fault- 

 rock," and in another in a cave ; and in the first place hematite is 

 interstratified with shale. At Dunamase there is an untried vein. 

 At Kilcolman silicious limonite occurs in an irregular mass, while 

 at Shanagolden it is in " fault-rock." In both counties the ores 

 occur in the Upper Limestone, close below the base of the coal- 

 measures. The production of the iron ore may possibly have been 

 due to the decay of the pyrites in the overlying coal-measure shales ; 

 as from this sulphate of iron would be formed and an insoluble 

 hydrated peroxide of iron — the first to pass off in solution, the 

 latter remaining to form the mass of ore. Or the peroxide of iron 

 may have accumulated in the limestone caves simultaneously with 

 the deposition of the coal-measure shales, a part of the clay also 

 being carried down to form the shales in the ore, a part of the iron 

 present going to form the ore and another portion the pyrite ; or 

 both processes may have occurred in turn. 



Some distance to the southward a cave was discovered in the 

 Ashford limestone quarry. It is on the same geological horizon 



