Kin ah an — On Irish Marbles and Limestones. 407 



In the hills between Leenaun and "Wesport, two or three miles 

 north-west of Sheffey, at and south-west of Lugaloughaun, are 

 three or four exposures of a peculiar rock that appears to be allied 

 to ophyte ; they are of different shades of light green. These 

 rocks work easily, but it is questionable if they could be procured 

 in large blocks. The place at present is very inaccessible. 



In Grlencullin, north-east of Mweelrea, is a dyke of mottled- 

 green rock allied to ophyte, or eklogyte (?). 



Sligo. 



At Slishwood and the valley running nearly south from Bun- 

 owen Bay, Lough Grill, is a band nearly two miles long and about 

 five hundred feet wide, of a dark-coloured, compact, somewhat 

 hard ophitic rock. It contains magnetite, especially to the west- 

 ward, where Hardman states it " possesses all the characters of 

 natural magnets." It also oontains some nickel. The rock is of 

 a splinter}'' nature. Although called a serpentine, it possibly more 

 correctly should be classed as an eklogyte. 



At Drumahaire, three miles north-east of the Slishwood ser- 

 pentine, there is a band about three hundred feet thick of very 

 similar rock, except that it is not " perceptibly magnetic." 



Close to Shanavan's Bridge, near Manorhamilton, is a third 

 band of similar rock, supposed to be about a mile long. 



In the Geology of Ireland, p. 191, it is suggested that these 

 rocks were possibly metamorphic Cambrians or even Laurentians. 

 It now, however, appears to be much more probable that they are 

 in part Cambrian, and in part Ordovician. 1 



Tyrone. 



Westward of Cookstown, to the north and north-west of 

 Pomeroy, are the hills in which Slieve Grallion is the principal 



1 If the markings found near Lough Finn, Co. Donegal, and exhibited by Dr. Hull 

 at British Association Meeting, 1886, are graptolites of Arenig types, as appears to 

 be very probable, the supposed Laurentians of Donegal are unquestionably metamor- 

 phosed Ordovicians, Arenigs, and Cambrians. Consequently, it is probable that the 

 rocks of Sligo, and also the similar rocks of Cos. Tyrone, Leitrim, and Mayo, are also 

 Cambrian, Arenig, and Ordovician. 



