Xlii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the idea which I have above suggested, that the phsenomena on which 

 such an opinion has been founded are only local. 



Finally, the author states the localities of the freshwater beds which 

 had been observed by himself and others. There are beds of this 

 kind on the east shore of Lake Huron 614 feet above the sea, and 

 others on the River Detroit, Lake Erie, and the River Niagara, at 

 nearly the same elevation. On the Ottawa are many deposits of 

 freshwater shells extending over a large area. Beds containing ma- 

 rine shells also range with them side by side. In Montreal Hill 

 there are also marine shells 470 feet above the sea, while about a 

 mile to the south there are freshwater beds at a level lower by some 

 hundred feet. 



The general explanation of phsenomena of this kind does not ap- 

 pear to me to present any serious difficulty, according to the general 

 views which I have expounded above. How far the striae and the 

 lines of dispersion may be generally characterized by the law of 

 divergency from a general central region, or may be more partially 

 characterized by divergency from particular centres, especially in the 

 more northern parts of the continent, are questions which can only 

 be answered by a far more detailed examination of the region lying to 

 the north of the great chain of lakes. Meanwhile we gladly accept 

 this paper of Dr. Bigsby's as a valuable addition to our knowledge 

 of the details of the erratic phsenomena of the district which he has 

 examined. 



Another paper on the subject of Drift and Boulders associated with 

 it has been brought before us by Professor Ramsay. It is entitled, 

 *' On the Sequence of Events during the Glacial Epoch, as evinced by 

 the Superficial Accumulations of North Wales." It will be recollected 

 that many years ago Mr. Trimmer made the important discovery of 

 marine shells in the Drift of Moel Tryfan at the height of 1392 feet. 

 These beds Professor Ramsay states to be continuous on the seaward 

 side of the mountain-range of Carnarvonshire. Between Cwm Seiont 

 and Llyn Padarn, there is a moorland tract covered with drift in which 

 the author found fragments of shells at the height of about 1000 feet. 

 Between Llanberris and Nant-Francon there is also a broad moor 

 covered with a great thickness of drift, stretching northwards along 

 the left bank of the Ogwen, and eastward into the valley of Marchlyn 

 Mawr, where it attains an elevation of 2000 feet. Corresponding 

 accumulations also rise on the opposite banks of the Ogwen into the 

 recesses of Carnedd Dafy and Carnedd Llewelyn, on their seaward 

 flanks, in some places to the elevation of 2300 feet. Patches of 

 similar drift also exist at equal altitudes at other points along this 

 range of mountains. The large blocks rest upon or are imbedded in 

 the smaller drift, and form, near the base of the mountains, a great 

 portion of the whole accumulated mass. They do not appear, how- 

 ever, to have travelled from this range into Anglesea, where, so far 

 as the author observed, the blocks are entirely of local origin. Very 

 large insulated boulders are sometimes found also on the tops or sides 

 of hills. 



Those portions of what is here described as Drift in the higher lo^ 



