EAMSAY DRIFT-PERIOD OF CANADA. 203 



drift that covers the plains of Canada and the northern States. It 

 is enough to say that the descriptions given by previous writers are 

 strictly correct. The whole country is literally covered with drift, — 

 to such an extent, indeed, that, except in denuded water- courses and 

 deep gorges, Kke those of the Genesee and Niagara, it is only in rare 

 cases that the rock is exposed. Even railway-cuttings rarely pene- 

 trate to the rocks below. It may be compared, in Europe, to the 

 northern plains of Germany. In horizontal extension it is the most 

 widely spread of all deposits ; and even in thickness it rises to the 

 dignity of a great formation, having by Logan and Hall been esti- 

 mated in places at 500 and 800 feet in thickness f. In all cases the 

 Laurentian boulders, which have often travelled hundreds of miles, are 

 mixed with fragments of the rocks that crop out northward towards 

 ihe Laurentine hills, and with stones from the strata of the im- 

 mediate neighbourhood, — ^the nimiber of the component materials of 

 the drift thus generally increasing to the south J, marking the fact 

 that the lowlands as well as the mountains have been subject to the 

 denuding and transporting agency of ice. At a distance from the 

 mountains, the boulders become comparatively few ; and it is this 

 admixture of calcareous and other material, often lightened with 

 sand, that fertilizes the soil in the great plains that surround the 

 lakes. 



The city of Ottawa stands on Trenton Hmestone ; and the surrounding country 

 is strewn with boulders of Laiu'entian gneiss and Trenton limestone itself, and 

 of Potsdam sandstone, &c. 



Between Ottawa, and Prescott on the St. Lawrence, the basement-rock is rarely 

 seen. The country is chiefly covered with gravel containing boulders of gneiss 

 from the hills, and of SHmian rocks from the plains. Here and there are 

 patches of sand containing pebbles and small boulders, generally rounded. In 

 some places it has the appearance of blown sand, — an effect that may have been 

 produced as the land emerged from the sea. 



The shores of Lake Ontario, in general, consist of low and shelving slopes of 

 drift ; but at Scarborough bold cliffs of sand, gravel, and clay partly white, with 

 boulders, rise 320 feet above the lake. The terraces of Toronto have been de- 

 scribed by Sir Charles LyeU. They are like those of the St. Lawrence and the 

 Ottawa. The lower part of the city stands on a very stiff boulder-clay, containing 

 large and small boulders, many of them scratched. Somewhat higher there are 

 beds of beautifully 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 Lakes Ontario, Erie, and Huron, the drift of gravel, 

 sand, and clay, with many large and small striated boulders, is frequently of great 



t I had an opportunity of examining the drift in many places between 

 Quebec and London (which lies between Lake Huron and Lake Erie), about 

 500 miles from If.E. to S.W. in a direct line, and from north to south between 

 Montreal and Ottawa, to Blossburg and New York. 



J See Miirray's Report, Geological Survey of Canada, 1856. 



VOL. XVI. PART I. Q 



