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XIII.— ON THE DIFFEEENT VAEIETIES OF IEISH PAVING- 

 SETTS. By PEOFESSOE EDWAED HULL, LL.D., 

 F.E.S., Director of the Geological Survey of Ireland. 



[Eead, February 17, 1886.] 



The Koyal Dublin Society seems the most suitable place for the 

 discussion of all questions connected with the industrial products 

 of Ireland, amongst which may be reckoned paving-stones. 



The production of paving-stones (or paving-setts, as they are 

 generally called) is comparatively recent in Ireland, as this 

 country has for a long time been dependent on imported stone, 

 particularly from North Wales, notwithstanding that there are 

 equally good sources of supply in various parts of Ireland itself. 

 The discredit of depending on a foreign supply for a material 

 which is abundant at home is happily being removed ; and it is 

 not improbable that, ere long, the course of this trade will be 

 reversed ; and that, instead of being a large importer, Ireland will 

 become a large exporter of this useful commodity ; in fact, I may 

 say that the current has already changed. 



In considering the question of the utilization of paving-setts, 

 we have first to consider their qualities; next, the varieties of 

 mineral composition and mode of formation; and, lastly, the 

 sources of supply ; which, as far as this Paper is concerned, will 

 be specially restricted to those now existing in Ireland. 



I. Qualities requisite for Paving-setts. — The qualities requisite 

 for paving-setts may be described under three heads : — 



{a) Uniformity of texture and composition, which we may 

 call " homogeneousness" ; 



(b) Toughness; and 



(c) Eoughness of surface. 



A few observations may be made upon each of these heads : — 



{a) Uniformity of Texture and Composition. — This is an essen- 

 tial quality in paving-setts, as it will be evident, on reflection, 



