.part 3] GLACIATIOX OF KORXH-EASTEUN IRELAND. 399 



•on the coast of Corbet Head. Here is a very interesting deposit 

 •of ealcreted gravel containing northern erratics (including Castle- 

 Espie limestone and Ailsa Craig eurite). The calcretion is due 

 to the very large quantity of Castle Espie limestone-boulders and 

 lobbies, many of which have been in part dissolved and have 

 provided the cementing material. 



The occurrence of the Tyrone rocks and Slieve Croob granite on 

 the shore of St. John's Point is probably due to beach-transport 

 along the shores of Dundrum Bay, as these rocks have not been 

 found in the Glacial deposits of the cliffs. 



(d) The Granitic Areas of Slieve Croob find the Mourne 

 Mountains. 



The mountain Slieve Croob (1755 feet O.D.) is made up of 

 indurated Silurian rocks on the northern edge of the granite intru- 

 sion ■which ranges from Castlewellan on the east to Slieve Gullion 

 •on the west, and forms a mass of high ground extending between 

 those points, cut however by the valley of the Upper Bann and by 

 the great trench which runs from the Lough Neagh basin to 

 Carlingford Lough, by way of Scarva, Poyntzpass, Newry, and 

 Warrenpoint. 



I shall deal first with the country bounded on the north by 

 a line running through Dromara and Gilford, and on the south by 

 Newcastle, Hilltown, and Newry. 



Although there is little direct evidence of this district having 

 been overridden by the Scottish ice, the phenomena observed in 

 the country immediately north and in the Mourne Mountains lead 

 me to believe that such was the case ; but so severe has been the 

 subsequent glaciation by the western ice that almost all the 

 materials of the existing drift have been derived from that direc- 

 tion, Avhile all the striated surfaces are such as would be produced 

 by an ice-sheet travelling from north-west to south-east. 



At Lawrencetown near Bannbridge are several small exposures 

 of red boulder-clay containing Tyrone rocks, together with Ter- 

 tiary basalt, chalk, and flint ; and between Lawrencetown and 

 Scarva the country is covered by mounds of similar material, 

 among which are several small lakes and peat-bogs which occupy 

 hollows in the drift-deposits. The surface of the country is 

 morainic in character. 



There are few good exposures in this part, but about half a 

 mile south of Scarva is a pit exposing some 30 feet of red boulder- 

 clay, the base of which is not seen. This pit is excavated in the 

 southern side of a mound, and at the southern end of the pit is a 

 thin bed of sand. The clay, which is very stony, contains Silu- 

 rian grit (local), basalt, flint, chalk, vein-quartz, Tyrone diorite 

 and red granite, red quartz-porphyry, Carboniferous sandstone, 

 Old lied Sandstone, and a large piece of silicified wood from 

 the Lough-Neagh Clays, from all of which it will be seen that the 

 material was clearly derived from the north-west. 



