378 Scientific Proceedings, Royal Dublin Society. 



part schistose (nietamorphic) . In N. E. Mayo, between Charles- 

 town and Ballaghaclerreen, in two places, there are beds of 

 impure limestone ; and in the Co. Tyrone, between Sixmile-cross 

 and Pomeroy, there are three or four beds of limestone. These 

 Silurian limestones have been utilized for lime, especially those in 

 South Mayo and Tyrone. Hydraulic limestones occur near Tour- 

 makeady. 



Limestones in the Ordovicians (Canibro or Loner Silurians) are 

 not very uncommon, having been recorded in the Cos. Wicklow, 

 Wexford, Waterford, Galway, Mayo, Sligo, Donegal, London- 

 derry, and Tyrone. All are more or less schistose (metamorphic), 

 and usually are not suitable for cut-stone purposes ; there are, 

 however, some stones in the Co. Donegal, that appear to belong to 

 this group, which have produced excellent work. All these 

 limestones are more or less utilized for lime, some of them being 

 hydraulic. 



Limestones of Cambrian age are found in Galway, and 

 probably in Donegal. There are also limestones in the Cos. 

 Londonderry, Tyrone, Sligo, and Mayo, in rocks that may be 

 metamorphosed Cambrians ; but the age of these rocks has not 

 been satisfactorily determined. These are all more or less meta- 

 morphosed, some also being chemically changed into Serpentine. 

 They are not in general good for cut-stone purposes, but beds both 

 in Galway and Donegal have been worked, and found to dress 

 well ; while some have also been worked as marble. The green 

 and variegated Serpentines of West Galway have been worked for 

 marble, and are well known in the market. The more general 

 purpose for which the Cambrian limestones are quarried is the 

 manufacture of lime. 



Lime. — As a general rule Irish limestones are suitable for the 

 production of lime, some of them being eminently so. The prin- 

 cipal exceptions are found in the Calp, some beds in which are so 

 arenaceous, or argillaceous, that they are rather sandstones, or 

 shales, than limestones. Some of these will not burn at all ; others 

 only with great care. 



The richest limes are produced by the White and Fenestella 

 limestones, some, indeed, being too rich for sound building pur- 

 poses, unless they are properly mixed with clay and sand. The 

 limes are almost invariably of a good white colour. 



