22 D. Mackintosh — Age of Floating Ice. 



lake. On the outer side the moraine rises about 20 feet above 

 the drift plateau. On the inner side the top of the moraine is 

 perhaps 40 feet above the level of the lake.^ 



Fig. 5. — Section of Marchlyn-mawr, 



From Bethesda to the highest Marine Drifts. — About Bethesda, and 

 in Nant Erancon, decided pinel may occasionally be seen ; but the 

 visible drift (probably underlain by pinel or brown clay, especially 

 at the lower levels) in the areas traversed by the Llafar, Caseg, and 

 Berthan, varies from a clayey loam, or rather loose foxy-coloured 

 loam, more or less charged with stones and boulders, to a rubbly or 

 gravelly loam, often so pack-full of stones as to assume their colour 

 ■when viewed from a distance. The stones are angular, subangular, 

 and occasionally rounded. They are either directly or indirectly 

 local, though many of them must have been floated to their present 

 positions irrespectively of the drainage of the country. Compara- 

 tively few of the stones are distinctly glaciated. The drift and its 

 stony contents presents the appearance of a heterogeneous accumula- 

 tion, resulting from the action of sea-waves washing down stones 

 and finer detritus from hill-slopes unfavourable to the exercise of 

 littoral attrition, to lower levels, combined with the dispersive 

 action of stone-freighted coast- or pack-ice. To these agencies we 

 must add the distribution by the sea and floating ice of precipitated 

 moraine debris. Indeed, in many places, as Professor Eamsay has 

 shown, the drift is chiefly spread out moraine-matter, and might be 

 called morainic marine drift. The existence of the drift on slopes, 

 ridges, and watersheds, proves that it could not have been spread out 

 by rains or small mountain streams ; while the fact of its stretching 

 up with smooth and flat outline to the higher ends of valleys shows 

 that its distribution could not have resulted from mere sub-aerial 

 glacial action. Moreover, the discovery of sea-shells in what must 

 be regarded as a downward extension of this drift by Mr. Trimmer, 

 and in similar drift near the Turbary by the late Mr. Griffith Ellis, 

 completes the evidence in favour of its accumulation under the sea. 



^ Professor Ramsay believes that this and a number of other lake-basins in North 

 Wales were formed by glaciers which terminated in the sea as the land was rising, 

 that they kept the marine drift out of the basins until they rose above the sea-level, 

 and that the glaciers finally melting the basins were occupied by fresh water. But 

 it may be asked, Did the cwms at the bottoms of which the lake-basins were 

 excavated contain glaciers before the sea (through the movement of the land) had 

 risen up to their levels ? or were they only occupied by glaciers after the sea had 

 retreated down to their levels ? 



