20 D. Mackintosh — Age of Floating Ice. 



boulders (chiefly at the bottom of the section), and many jDebbles in 

 the gravel, which may have been worked up from their parent rocks 

 on the N.W. side of the hill by waves and coast-ice as the land was 

 sinking ; but a large percentage of the pebbles certainly, and some 

 of the large boulders probably, were derived from the far N. The 

 stones in general are subangular, and consist of felstone deeply 

 weathered white, from the N.W. side of the hill ; porphyry partly 

 from the N.W. side of the hill, and partly, I believe, from Cumber- 

 land ; local slate ; several kinds of granite from Cumberland and 

 Scotland; felspathic breccia and ashes from a greater or less distance; 

 quartz and a rock resembling gneiss from the N.W. side of the 

 hill (?) ; etc., etc. Among the granites there are many pebbles and 

 some good-sized stones of very decided Eskdale and Criffell granite. 

 The latter (which must have travelled no less a distance than 130 

 miles !) is generally of the same kind as the principal variety 

 found in the drifts of Cumberland, Lancashire, and Cheshire, and is 

 a perfect facsimile of granite now quarried by the Messrs. Newall 

 at Craig Nair, near Dalbeattie.^ The Eskdale granite embraces 

 several varieties with which I was familiar on the E., W., and N. 

 sides of Eskdale, and between the latter and Wastwater foot ; it is 

 likewise of the same kinds as those found in the Lancashire and 

 Cheshire drifts. These granites must have been carried to near the 

 top of Moel-y-Tryfan by rafts of coast-ice when the land was too 

 deeply submerged to permit any granite falling on the surface 

 of glaciers terminating in icebergs. Indeed, there is some difficulty 

 in seeing how even coast-ice could have picked up granite from the 

 Eskdale fells at a height of nearly 1400 feet above the present sea- 

 level. The difficulty might be obviated by taking into consideration 

 the progressively-upward action of sea-waves and coast-ice on 

 Moel-y-Tryfan, were it not that I failed to see any granite pebbles 

 on the hill-slopes at a lower level, though such may possibly exist.^ 



Fig, 4. — Distant View of Moel-y-Tryfan, from near Bangor. 

 Alexandra Quarry to the left of the summit. 



The N.W. side of Moel-y-Tryfan is covered with drift varying 

 from loamy sand to hard pinel, being often a mass of subangular or 



1 The Shapfell and Dalheattie Company are quarrying granite near Dalbeattie of a 

 somewhat different kind with a tendency to run into groups of oblong crystals 

 of felspar of a more or less brownish hue. 



2 Mr. Trimmer, in his Geology (1841), mentions the existence of graiiitic detritus 

 at eight points between the Menai Strait and Snowdoii, but he only specifies Moel-y- 

 Tryfan, and says nothing, so far as 1 cau remember, about the character of the 

 granite. 



