204 



PEOCEEDIN^GS OF THE GEOLOGICAL SOCIETY. 





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and unknown thickness. White clay occurs round Lon- 

 don ; from this the bricks are made of which the town is 

 built. The geologist may here travel twenty or thirty miles 

 without seeing rocks in place. In the gravels near Hamilton, 

 elephantine remains were found, supposed by Dr. Dawson 

 to have been washed from the table-land of the Niagara 

 escarpment when the lower plain was still covered by sea. 



Between Rochester and Scottsville, the undulating sur- 

 face consists entirely of drift, containing numerous boul- 

 ders of Potsdam sandstone, labradorite, gneiss, hyper- 

 sthene-rock, &c., from the Laurentine Chain about 100 miles 

 off. Many of them are large, smooth, and well striated. 

 Mr. Hall observed that the drift is here often 120 feet thick, 

 and that the mounds are steepest to the north. 



The River Genesee runs through a deep rocky ravine, 

 which near Portage is 350 feet high. The rock on the top 

 is smoothed and scratched, and along the whole course of 

 the river, on either side above the gorge, the rocks are 

 generally obscured by drift. On this river Dr. Bigsby ob- 

 served fragments from Montreal Mountain, which lies 270 

 miles to the north-east ; and Laurentine boulders are com- 

 mon. I observed at Mountmorris, on the river, that in 

 the lower part of the drift the stones are often angular and 

 scratched, while the upper beds are of sand. 



Near Portage, on the Genesee, the drift is said by Mr. 

 Hall to be about 500 feet thick, filling up a valley in 

 the rocks, through which an older river ran previous to 

 the drift-period. When the country emerged from the 

 sea, and a new drainage was formed, the river was turned 

 aside by this accumulation, finding it easier to form a 

 new channel in the present gorge, 350 feet deep. 



At Onondaga the drift is 640 feet thick. 



Drift is equally characteristic of Connecticut and Mas- 

 sachusetts. In the New Red Sandstone Valley of Con- 

 necticut, the drift seemed mixed, but mostly local. 



It is also well known that large far-transported boul- 

 ders occur on the south bank of the Ohio, — a circum- 

 stance less remarkable than at first sight appears, when 

 we consider that it is stated that icebergs have been seen 

 as far south as the Azores. 



Wherever the drift is freshly removed, the 

 rocks are found to be smoothed, striated, and 

 often rounded. On the Isle Perrot, near Mon- 

 treal, Mr. Billings observed striae running S.W. ; 

 and near Ottawa, by the river, in several places 

 they run south-easterly. These instances are 

 both at low levels ; and during a late period it is 

 easy to understand how, during a former exten- 

 sion of the Gulf of St. Lawrence, icebergs drift- 

 ing up the Gulf, as they do now, would produce 

 scratches running S.W. in the strait between the 

 Laurentine hills and the Mountains of Adirondack, 

 while in the open sea south of Ottawa (now a 

 great plain) the drift passed in an opposite direc- 

 tion. About halfway between Ottawa and Pres- 

 cott, on the St. Lawrence, near Kempville, the striae 



