1873.] CAMPBELL — GLACIATION OF IRELAND. 199 



a general N.E. and N.W. extension, and cross meridians from 6° to 

 10° west, diagonally between latitudes 51° and 56° north. There 

 must be some reason for the shape of the coast and surface of this 

 part of the earth's solid crust. 



III. Under Water. — Beyond high-water mark in harbours the 

 sea now packs layers of mud and shingle in rocky hollows ; but 

 near the coast, and far out at sea, peaks of rock stand up in the 

 midst of undulating plains of drift, of which the charts give the form 

 in fathoms below the plane of the water. The limit of 600 feet is 

 far from shore. The sea-bottom about Ireland is an undulating 

 plain with rocky hills in it, very like plains on shore. 



IY. On Shore. — The greater part of the area of Ireland consists 

 of low undulating rock-surfaces, covered with Boulder-clay, with 

 water drifts of sand and gravel, with soil and peat-bogs. Amidst 

 this cover of loose materials stand groups of bare rocky mountains, 

 and isolated hills, knolls, and hillocks of solid rock. The highest 

 point in Ireland is 3404 feet above the sea-level, near Killarney, in 

 the S.W. So far as my own observations and my reading enable 

 me to form an opinion, the present shape of all the rock-surfaces in 

 Ireland, from the highest tops to the sea-level, is the result of wear- 

 ing and waste ; and the shape of the low lands is the result of 

 packing fragments, broken, crushed, ground, or worn off solid rocks. 

 Some great denuding engines must have worked on this region. 



As the drift is commonly " glacial " next to the rock, and as most 

 of the rock-surfaces in Ireland still are " glaciated " where they 

 have been protected from water and weather, I attribute the pre- 

 sent shape of the surface of Ireland chiefly to glacial action during 

 a geological period later than the formation of the Antrim chalk. 



V. Denudation*. — That large masses of solid rock have been 



* On the day before this paper was read, Professor Ramsay was kind enough 

 to lend me a map marked with the broad arrow of the Ordnance Survey, and 

 thus described on the face of it : — 



" Map of Ireland to accompany the report of the Eailway Commissioners, 

 1838, &c, &c. ; engraved under the direction of Lieut. Larcom, Eoyal Engineers, 

 May 1837 (in MS.). Coloured to represent portions of Ireland which would be 

 above water if it was depressed 500 feet, and to show the positions of the escars 

 and gravel deposits with reference to the islands which would be formed. Signed 

 Henry James, Capt. Eoyal Engineers." 



This map was placed beside a geological map of Ireland to show that eleva- 

 tions and depressions do not coincide with local geological disturbances, but 

 with " surface denudations." The map, coloured black on a blue ground, shows 

 two groups of more than 450 small islands. Their shape is irregular ; but long 

 narrow points trend south-westward; blunt ends are generally towards the 

 north-east, and cliffs face the Atlantic and the north-west. Beside these maps 

 were placed a travelling map, with notes of observations made in Ireland, and 

 shaded Ordnance maps of Scotland, with thick ice, drawn to scale. Coast-lines 

 of the supposed Irish archipelago correspond to many inland cliffs. " Drum- 

 lins," escars, osar, kames (Gaelic "ceum," a foot-path), and ridges of drift de- 

 scribed by Messrs. Close & Kinahan, mentioned in this paper, shown on shaded 

 Ordnance maps, and conspicuous in all glaciated countries known to me, are 

 shown here to correspond in direction to the probable run of tides in sounds 

 and wide passages less than 500 feet deep. These now are passes, hollows, low- 

 lands, undulating plains of sands and gravel, bogs and large lakes, in Ireland ; 

 the islands now are isolated rocks with the shape of " Crag and tail," and 



