434" Royal Irish Academy, 



rounded fragments of coal in certain grit beds of the coal forma- 

 tion, from which we learn that some of the older beds of coal had 

 assumed an indurated state before the deposition of the more re- 

 cent strata of this great formation, the total thickness of which in 

 South Wales is 12,000 feet. At Penelawdd, on the Bury river near 

 Swansea, Mr. Logan first found, in 1839, a rounded pebble of can- 

 nel-coal in a bed of clay ; he subsequently discovered that in the 

 Pennant grit of Kilvey Hill, near Swansea, there are many con- 

 glomerate beds containing pebbles of coal, intermixed with sand 

 and pebbles of ironstone, and very rarely with boulders of granite 

 and mica-slate. The pebbles are chiefly of common bituminous 

 coal ; two only have been found composed of cannel-coal, the only 

 seams of which known in the lower coal-measures are 2000 feet 

 below the Pennant grit. Mr. Logan believes that coal-pebbles oc- 

 cur throughout the whole mass of the Pennant sandstone, the thick- 

 ness of which is 3000 feet, but he has seen no such pebbles in the 

 lower coal-measures. 



Mr. Buddie has lately found similar pebbles of coal in the Pen- 

 nant grit of the Forest of Dean. 



(To be continued.) 



ROYAL IRISH ACADEMY. 



January 11, 1841.— Tlie Rev. Thomas H. Porter. D.D., read a 

 paper " On the Deposits of Gravel in the Neighbourhood of Dublin." 



After detailing the facts commonly known as to the stratified beds 

 and ridges of limestone gravel, lying over the great central limestone 

 region of Ireland, and the continuance of deposits containing a large 

 proportion of rounded pebbles and stones of the same material, over 

 the granite and other primitive rocks to the eastward of the lirflestone 

 country, it was argued that there were clear indications of a great 

 diluvial action from west to east, by which the surface of the limestone 

 was reduced to its present level, and the remains of its upper portions 

 spread over the limestone region itself, and carried eastward to the sea. 

 The occurrence of similar calcareous deposits in the seaward glens and 

 valleys of the Dublin and Wicklow mountains for some miles south, 

 and on their sides to a considerable height, was ascribed to the cur- 

 rent of the same deluge, sweeping the transported substances over the 

 lower parts of the mountain range, and then turning southwards along 

 the sea coast, after passing the north fiank of the mountains. Similar 

 facts, but in an inverted order, from south to north, have been observed 

 towards the southern flank, in the County Wexford. 



It was urged, that the subsiding waters of this inundation, rushing 

 down the valleys, and meeting below with the main current on the 

 plains, would throw up those ridges along the sides of the hills, and 

 on the flats beneath ; of which a remarkable example is presented in 

 the glen of Ballynascorney (through which the Dodder descends 

 from the Dublin mountains), and in the gravel hills in front of that, 

 from Tallaght to Crumlin. 



The direction assumed in this paper for the diluvial current agrees 

 remarkably with that assigned by Professor Phillips as the cause of 

 the distribution of the Shapfell boulders over the north-east of Eng- 



