34 Ihc Irish Naturalist. February 



to within a half-mile of the latter. Among the miscellaneous 

 plants of the eastern lake-shore were Trifoliuni mcdiuvi and 

 Solanuvi Dulcamara. 



Islands are rather numerous alono- the eastern side of the 

 lake, and it might have been expected that here the limestone 

 flora would have attained a striking development, as on the 

 adjoining Lough Carra. This proved to be not the case. The 

 weather did not permit of an examination of all the islands, 

 but a number, extending from Castle Hag, at the mouth of the 

 Robe River, to Carrigeennasassonagh, oif Devenish, were 

 visited, and ma}^ be taken as a sample of the whole. These 

 islands are ridges of drift, their long axes lying N.E. and S.W. 

 This drift has been derived not so much from the limestone 

 as from the sandstones and slates lying to the north and 

 west. The matrix is not highl}' calcareous, and limestone 

 figures only sparingly in the blocks on the shore. On the larger 

 islands the central portion is occupied by a plateau of Boulder- 

 cla}^ tree-covered or cultivated, with a steep scarp descending 

 to a broad shelf, clothed with trees or bushes, sloping to the 

 water, mostl}^ thickl}^ strewn with blocks of the afore-men- 

 tioned rocks (fig. i). On the smaller islets the waves have 

 swept right across, and only a ridge of stones and blocks, the 

 wreck of the drift, remains. 



— --T"*--' ~> 





^.o--.., 



Fig. I.— Section of Deveuish, Lough Mask, showing Boulder-clay 

 core, with ruined church, and old beach invaded by wood. 



Knowing that drainage operations had been in progress 

 around Lough Mask and Lough Corrib about 1840 or 1S50, 1 at 

 first put down this old water-level to pre-drainage denudation. 

 But the Ordnance maps, and also information obtained locally, 

 show that the effect of the engineering operations (which con- 

 sisted chiefly of the cutting of that lunatic canal across the 

 limestone, v.liich naturally has a bottom like a sieve) was to 

 lower the water-level only two feet. Now the old beach is 

 from ID to 15 feet above present storm level. The drainage 

 from the lake is still, as it has always been, subterranean. 



