Glacial Phenomena of Canada, 



329 



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fully laminated brick-clays, similar to the clay of 

 the Hudson Valley, afterwards to be described, and 

 probably its equivalent. In 1857, great railway- 

 cuttings were in progress in the lower clay. The 

 terrace marked * in fig. 2 consists of sand with 

 Laurentian and other boulders resting on white 

 brick-clay, which is beautifully laminated, and in 

 which similar boulders are more sparingly scattered. 



The removal of the sand by denudation, to form 

 the terrace, has produced a great concentration of 

 gneissic and other boulders on the surface between 

 the terrace and the lake. 



In the great plains between Lake Ontario, Erie, 

 and Huron, the drift of gravel, sand, and clay, with 

 many large and small striated boulders, is fre- 

 quently of great and unknown thickness. White 

 clay occurs round London ; and from this the bricks 

 are made of which the town is built. The geo- 

 logist may here travel twenty or thirty miles with- 

 out seeing rocks in place. In the gravels near 

 Hamilton, elephantine remains were found, suppos- 

 ed 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 undulat- 

 ing surface consists entirely of drift, containing 

 numerous boulders of Potsdam sandstone, labra- 

 dorite, gneiss, hypersthene-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 35u 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. Bigby observed frag- 

 ments from Montreal Mountain, which lie3 270 

 miles to the north-east ; and Laurentine boulders 

 are common. I observed at Mount-morris, 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 



