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PKOCEEDINGS 0E THE GEOLOGICAL SOCIETY. [April 30, 



lying boulder-beds ; in otber places tbe latter rests on an eroded 

 surface of the former, and both are overlain by Boulder-clay of the 

 Drift-period (see figs. 1 & 2). The blocks of grit, derived either 

 from the Silurian or Old-Red-Sandstone formations, lying to the 

 northward, are sometimes from 18 inches to 2 feet in diameter, and 

 are not unlike those found in the Boulder-clay of the Glacial period, 

 though we failed to discover any very clear marks of ice-action on 

 their surfaces. It is difficult, however, to conceive how blocks of 

 such size, and so irregular in shape, could have been transported for 

 a distance of 20 or 30 miles (the nearest distance of their original 

 positions), except by the agency of floating ice ; and the absence of 

 ice-grooves and scratches on boulders of sandstone which have 

 undergone a certain degree of decomposition from their proximity to 

 the surface, cannot be regarded as a serious objection to the view 

 that the boulders themselves have been carried on ice-rafts. 



Position of the Boulder-beds. — On referring to Griffith's Geological 

 Map of Ireland, it will be seen that the city of Armagh stands in 

 proximity to beds but little removed from the base of the Carboni- 

 ferous Limestone. There are, however, representatives of the New 

 Red Sandstone, which were observed by Mr. Egan in wells and 

 excavations beneath the centre of the city itself. As the Permian 

 beds dip in that direction, they no doubt pass below the New Bed 

 Sandstone ; so that their geological position is beyond question as 

 regards this formation (see fig. 3). 



Fig. 3. Horizontal Section through the City of Armagh (1 m ile). 



a. Drift. 



c. Permian Boulder-beds. 



h. New Eed Sandstone, resting on c. 

 d. Carboniferous Limestone. 

 e. Lower Silurian Eocks. 



Their relations to the Carboniferous Limestone can also be clearly 

 determined at the quarries where the boulder-beds themselves are 

 seen. They lie upon beds within 300 or 400 feet of the base of the 

 Carboniferous Limestone, which is worked in numerous quarries in 

 the vicinity. These quarries are celebrated for the number and 

 variety of the fish-remains they have afforded, including some of the 

 type specimens of Agassiz's ' Poissons Eossiles,' now in Lord Ennis- 

 kiUen's collection. 



Denudation of the Carboniferous Beds. — As in the north of England, 

 so in the north of Ireland, the amount of denudation which the 

 Carboniferous rocks have undergone before the deposition of the 

 Permian rocks, has been very great. In the case of Armagh, the 

 whole of the middle or " Calp " series, the Upper Limestone, the 

 Yoredale shales, Millstone-grit, and Coal-measures (which are largely 

 developed to the north of Dungannon) have been removed — a total 



