part 3] GLACIATION OF XOETH-EASi'ERX IRELAND. 395 



-clay which contains erratics of Tertiary basalt, chalk, flint, and 

 purple porphyrite, all from the Antrim coast on the north, also 

 gneiss, Silurian grit, quartzite, schist, quartz- porphyry from 

 Drumadoon Point and pitchstone from Corriegills (both in the 

 Island of Arran), and Ailsa Craig eurite. There are also sections 

 in similar material along the coast of Belfast Lough, near Helens 

 Bay and Carnalea. 



Between Bangor and Orlock Point the coastline is a low plat- 

 form of Silurian rocks, apparently a raised-beach platform ; but 

 inland of this are low cliffs, capped in places by red boulder-clay. 

 On the raised-beach platform are numerous boulders of dolerite 

 and basalt, some of which are of considerable size, and pebbles of 

 Ailsa Craig eurite are frequently met with. 



In the country between the northern coast and the Dundonald 

 Valley are many drumlins, the axes of which, for the greater part, 

 lie north and south. 



There is comparatively little of the sandy and gravelly material 

 which forms so conspicuous a feature of the drifts of the Bann 

 Valley and the Lough Neagh Basin ; but there are mounds of 

 sand and gravel at Bangor Castle, and south-east of it gravels 

 also occur at Drumkirk and beneath the town of Newtownards. 



In the Dundonald Valley are large quantities of sand and gravel 

 disposed in irregular mounds. These are undoubtedly the product 

 of the Scottish ice, as they contain a number of Scottish rocks 

 (including that of Ailsa Craig). 



Near the road- junction a mile east of Dundonald is a disused 

 quarry in Triassic sandstone, covered by about 30 feet of red 

 sandy drift consisting largely of reassorted Trias. The section is 

 in the side of a mound of drift, and the following erratics are 

 present : — basalt, flint, .chalk, purple andesite, drusy granite from 

 Arran, several varieties of decomposed granite with plentiful black 

 mica (probably Scottish), and Ailsa Craig eurite. At the western 

 end of this valley these deposits pass into a red sand with very few 

 stones, similar to the Malone Sands of the Belfast Valley. 



The country between Scrabo Hill and Comber is covered with 

 drumlins of red sandy boulder-clay, containing Scottish erratics, 

 the local Silurian grits, and the dolerites of Scrabo Hill. The 

 last-named are present in great numbers, and are of large size 

 and angular to subangular form. 



(b) The Ards Peninsula and Strangford Lough. 



The Ards Peninsula is a low-lying tract of land between Strang- 

 ford Lough and the sea, and in no part reaches the 200-foot 

 contour, except near Portaferry, where an isolated hill reaches 

 339 feet. The surface is covered by drumlins, containing Scottish 

 rocks, with boulders of basalt and the local Silurian grits and 

 slates. 



In the area north-west of Gre} r Abbey are numerous boulders 

 of the Scrabo Hill dolerite, and of these, one known as the 



