374 Proceedings of the British Association. 



is north-east and south-west, but in some parts of Tyrone it is 

 more north and south. In the south the direction approaches 

 more to the east and west. At Dunmorehead, county of Done- 

 gal, the quartz-rock exhibits a concretionary structure similar 

 to that of orbicular granite, and is often mistaken for a trap- 

 rock. The limestone beds associated with the schists of Done- 

 gal are not continuous, though they occur in certain lines. 

 They are sometimes cut off by trap-dikes, and then become do- 

 lomitic. The primary district of Mayo and Gal way is similar 

 to that of Derry and Donegal. Mr Griffith proposes to divide 

 the transition slates of Ireland into groups, as soon as the state 

 of the science enables him to do so. In the newer portion of 

 these deposits occur alternations of sandstone and clayslate; and 

 again a limestone similar to that of the Blackwater, and contain- 

 ing organic remains, alternates with the upper part of the schist ; 

 and, as in this latter case the limestone contains fossils of the 

 mountain limestone, the schist which alternates with it must 

 also be of comparatively recent origin. A section from Dun- 

 garvon to Carrick was exhibited, and another in Waterford. 

 The old red sandstone is considered by Mr Griffith as divisible 

 into two or even three parts, viz. 1st, The common old red ; %d, 

 A white variety which occupies a central position ; and, 3d, A 

 sandstone which alternates with the oldest part of the coal for- 

 mation. In the county of Mayo there are beds of the sandstone 

 alternating with limestone. Though there seems to be a tran- 

 sition from the limestone to the sandstone, yet there are always 

 portions of the formations where in the one all the strata are of 

 limestone, and in the other of sandstone. The mountain lime- 

 stone formation extends from the county of Cork to Fermanagh, 

 and occupies two-thirds of Ireland. A section from Newcastle 

 in county Down to Benbulbin in Sligo, was exhibited. A sin- 

 gular cavern occurs in the limestone under the mountain of Kul- 

 keagh. It contains no stalactites or stalagmites, but its sides 

 have a remarkably smooth and polished surface. Mr Griffith 

 regards the calp of Kirwan as the lowest bed of the mountain 

 limestone, but as a member of the series which ought to be dis- 

 tinguished from the series of Benbulbin. The calp rarely if 

 ever contains fossils. Mr Griffith next described the various 

 coal-fields of Ireland, beginning with those of the south, and 



