394 MAJOR A. E. DWERKYHOTTSE ON THE [vol. lxxix,. 



excavated in a mound. Basalt and chalk appear to be the sole: 

 constituents of this deposit. 



Running parallel to the railway along the valley of the River- 

 Main, from a point 1 mile south of Glarryford Station to 1 mile 

 north of Dunloy Station, is a long ridge of gravel, which in places- 

 disappears below the surface of the bog for short intervals, but is- 

 otherwise continuous over a distance of 7 miles. Sections in the 

 ridge reveal a coarse and very dirty brownish gravel, consisting 

 for the greater part of basalt, but also containing a considerable 

 quantity of rhyolite similar to that which occurs in situ at Clogfu 

 This ridge is an esker, and occupies the line which one would 

 expect a sub-glacial river to f oIIoav. It can be traced right up to. 

 the watershed at the head of the Main, and is continued north- 

 wards by an overflow-channel, deeply cut into the hasalt, and 

 falling into the valley of the northward-flowing Glenlough River. 



Near Caldanagh Bridge, west of Dunloy, are many large boulders 

 of the local basalt scattered over the country, and I found one 

 erratic of epidiorite (Tyrone) and one of white Carboniferous- 

 sandstone similar to that of Slieve Gallion. 



Mounds of drift tail off northwards from the end of this hill, 

 and west of Tullaghans Burn is a long north-and-south ridge, 

 which is the continuation of the lateral morainic accumulations 

 between Portglenone and Hyndstown. 



The watershed between the Main and its tributaries on the one 

 hand, and the northward flowing streams on the other, crosses the 

 railway about 3 miles north of Dunloy Station, and passes east- 

 wards by Kendals Hill to the northern spur of Slievenahanaghan. 



Between this watershed and the valley of the Bush River and 

 the Breckagh Burn, running along the southern foot of the 

 great Annoy moraine, is a series of big drift-mounds containing 

 erratics from the south and occasional pebbles of Ailsa-Craig 

 eurite. 



VII. Cor:s T TT Down. 



The County of Down falls into four natural divisions : (a) a 

 northern portion comprising the country around Bangoi', Donagh- 

 adee, Mill Isle, Conlig, and Holy wood; (b) the Ards Peninsula; 

 (c) the Silurian uplands extending from Comber to Dundrum, 

 and from Poj'ntzpass to Downpatrick and the mouth of Strangford 

 Lough ; and (d) the granitic mountains of Slieve Croob and the 

 Mournes. 



(a) The Northern Area. 



This area is bounded on three sides by the sea, and on the south 

 by the deep valley partly filled by Trias running from Belfast by 

 way of Dundonald, Comber, and the head of Strangford Lough to 

 Grey Abbey. 



Along the line of the Belfast & County Down Railway from 

 Holvwood to Bangor are numerous sections in tough red boulder- 



