192 3- Reviei£>s. 12-j 



moraines of the last advance of the Scottish ice, and also of the j^ravel 

 terraces of the Carey River, a more detailed account of whicli will be 

 found in the forthcoming Survey Memoir on the I^allycastlc district. 

 The description of the frontal moraines of the Donegal ice-sheet in the 

 ]")ungannon-Cookstown area standing " rank behind rank for several 

 miles " is so striking that one would wish that the subject had been 

 dealt with at greater length b\' the author. 



In addition to his work on the drifts and their included erratics, Major 

 Dwerryhouse has made a special study of the temporary lakes of late 

 Glacial times, and their accompanying and resultant overflow or drainage 

 channels. While the ice-sheets, which had invaded north-eastern Ireland 

 either from the north or from the west, retreated towards their sources, 

 temporary lakes were formed by the water from the melting ice being 

 impounded between the slopes of the hills and the ice-sheets, and when 

 the water of these lakes could find its way over a col or along the hillside 

 towards ice-free country, it rapidly cut a ravine or overflow channel to 

 the extent of its powers of erosion. With a farther retreat of the ice, 

 ways of escape at lower levels were opened, the level of the water in the 

 lake fell, and the temporary drainage channel was then abandoned. In 

 any mountainous country which has been invaded by an ice-sheet these 

 temporary drainage channels and hill-side gashes occur in great numbers, 

 and we are introduced to some hundreds of them in the course of the 

 paper, which is effectively illustrated by many figures and plates dealing 

 with this interesting type of temporary erosion. Jn the Ballycastle 

 district Major Dwerryhouse has mapped some striking examples of these 

 drainage channels. When the seaward end of Glendun was tilled with 

 Scottish ice, the waters of the lake which had been formed in tlie upper 

 portions of the valley could only escape towards the north by the 

 comparatively ice-free valley of the Carey river, and the main road from 

 Cushendun to Ballycastle now runs along the floor of the drainage channel 

 which the outflowing waters of the lake had cut into the lowest portion 

 of the ridge which separates Glendun from the lowlands south of Ball\- 

 castle. Another great drainage channel in this district is the Invcr 

 gorge, which carried away to the south-west the overflow waters from 

 the lakes which had been formed to the east and south-east of Knocklayd. 

 In the Slieve Gallion district the author has noted the very striking glens 

 of Carndaisy and Gortanewry which he considers to be the drainage 

 channels that carried the overflow of the temporary lakes of this district 

 eastward and northward towards the valley of the Bann. 



The Mourne Mountains have also yielded instances of these channels, 

 and in the deep flat-floored narrow valley which connects Portadown 

 with the head of Carlingford :Major Dwerryhouse sees the drainage 

 channel of the Lough Xeagh basin during the time when the presence 

 of the Scottish ice south of Coleraine prevented the escape of the waters 

 of that basin towards the north. In Carlingford many drainage channels 

 have been mapped, the most important being that which carried the 

 overflow water of the Jenkinstown (glacial) lake into Glenmore. There 

 are numerous channels on the slopes of Barnavave and Slieve-na-glogh 



