102 Scientific Proceedings, Royal Dublin Society. 



in the immediate vicinity. Near the old gateway at Mellifont, 

 and in other places in that part of the county, there is a dark-gre}' 

 compact slate, with a tendency to split into laminae. " This, if 

 properly worked, would be a very useful and good material for 

 many purposes, as it admits of division to any moderate thickness 

 required." ( Wilkinson.) 



MAYO. 



As in the adjoining county of Gralway, the slate rocks in the 

 Arenigs, Ordovicians, and Silurians of Mayo are often more or less 

 metamorphosed into schists. Slate rocks also occur in the Lower 

 Carboniferous and the Coal-measures. 



In the areas in which they are found the older slates and schists 

 are very generally used for ordinary building purposes, sandstone 

 and limestone being used for the cut work. They are very varied 

 in character. " West of Swineford the slate rocks have vertical 

 cleavage and joints, and subdivide, when much exposed, into large, 

 flat-bedded masses, standing on edge. A peculiar mass of rock of 

 this kind appears above the surface, a few miles north-west of 

 Swineford, and, from the large square-shaped and moderately 

 thick beds of the rock, presents such inviting and ready-prepared 

 materials for walls of great magnitude as almost to cause a wish 

 that the available powers of the present day should make some bold 

 use of them." ( Wilkinson.) According to Symes, the splitting into 

 these cyclopean slabs have been produced by water freezing in the 

 cleavage divisions. Slates that have been used for roofing purposes 

 occur in places previously mentioned. 



MEATH. 



The slate rocks occur principally in the northern part of this 

 county, and have been extensively used in Kelts, both in ancient 

 and modern times, the stone generally used being more or less 

 gritty. St. Columbkille's house, at Kells, as also the round castle 

 there, are built of a hard, durable rock, that does not admit of much 

 working. A similar stone is found in the old church and round 

 tower at that place, but mixed with limestone, the cut-work being 

 of sandstone. In the quarry to the east of Kells the stone is 

 exceedingly hard and brittle, rising in angular and wedge-shaped 



