1 68 'I he Irish Naturalist. September, 



The great sea-loughs of Sheep Haven and Mulroy Bay, 

 visited during the Conference, represent submerged river- 

 valleys flooded during the last depression of the land, though 

 it is possible that Mulroy Baj^ may have been modified by ice 

 action during the Glacial Period to such an extent that it 

 might be better considered as a submerged rock-basin, the lip 

 being represented by " The Narrows," a narrow winding 

 channel with a depth of only two fathoms on the bar, as com- 

 pared with the fourteen fathoms reached farther inland. 



That there has been an elevation of the land during recent 

 geological times in the district around Sheep Haven is shown 

 by the curious relations of Horn Head and Rosguill penin- 

 sula to the mainland. Horn Head is so loosely attached to 

 the mainland by the causeway at Dunfanaghy as to be in 

 realit}' an island, and Rosguill peninsula is a collection of 

 islands running from Carrigart to Melmore Head, and con- 

 nected with each other by low rock-ledges and blown sand. 

 Tranarossan, visited during the Conference, is the most 

 striking of these. 



On the excursion to Rosguill and Melmore Head the Lough 

 Salt series of rocks was seen in fine sections, the quartzites 

 (Plate 6) of the Murder Hole and the relations of the granite to 

 the metamorphic rocks being especially striking. During the 

 excursion to the district in which the Lough Salt series is 

 typically developed, the part played by solution in the forma- 

 tion of lakes and rivers was seen in Lough Salt itself and in 

 the river that flows out of it to the north. Lough Salt 

 Mountain is composed of quartzite, and from its summit a 

 very extensive view^ can be obtained, including practically 

 the whole of north-western Donegal. On the road to Lough 

 Salt through Glen, and from Lough Salt to Creeslough by 

 Barnesbeg; the granite chain of Glendowan was crossed, and 

 splendid examples of foliation were observed, as well as many 

 examples of inclusions of mica-schist, limestone, and quartz- 

 ite in the margins of the granite. In the very fine transverse 

 valley of Barnesbeg a magnificent section of fine-grained grey 

 granite may be seen interbedded with schist, the grey granite 

 being replaced in its lower portions by a salmon-coloured 

 one rich in quartz. The return along Glen Lough showed 

 a rather remarkable instance of a narrow lake some miles in 

 length being fed by streams at both ends and discharging 



