100 Mr. Maclure on the Geology of part of N. America. 



Island, would not have been accumulated at this period, and 

 the current now called the Gulf Stream, would have then 

 most probably run along the foot of the chain of mountains. 



The continent east of the Stoney Mountains, and south of 

 the north edge of the great lake, would then consist of an 

 immense lake, surrrounded on the east and south side by a 

 strip of high land from one hundred to two hundred miles 

 broad; the rain falling upon which would partly fall into the 

 lake and partly into the ocean, through small rivers, along 

 the mouths of which navigators might have in vain searched 

 for rivers proportionate to the apparent extent of the conti- 

 nent, as they now do on^the coast of New South Wales, for 

 rivers capable of draining so extensive a country. 



The passage of the St. Lawrence through the high ridge 

 between Quebec and Montreal, must either have been torn 

 asunder by an extraordinary convulsion, been always in that 

 state, or it must have been worn down by the gradual butcon- 

 tinued action of running water, aided by the friction of all the 

 substances it carries along with it ; the undisturbed regularity 

 of all the surrounding strata both on the banks of the St. Law- 

 rence and Hudson, renders the first supposition improba- 

 ble ; on the second supposition that the river had always 

 run freely through the passage in those mountains, it must 

 follow that the river had always run in its bed from Lake 

 Ontario to Montreal, and from the weight of water and ra- 

 pidity of its current,^ for so long a time, must have worn 

 down a deep channel, and buried itself between high and 

 perpendicular banks ; but this does not correspond with the 

 actual state of the river, which from the lake to the rising 

 ground above Montreal runs in a bed very little below the 

 level of the surrounding country, nor does either the present 

 situation of the river or its banks, warrant the supposition 

 that the action of the current had continued so long : by 

 the same supposition the level of Lake Ontario must have 

 always remained as far below the level of Lake Erie as at 

 present, and the waters must have constantly fallen over the 

 ridge at Niagara ; but the small progress it has made in 

 wearing away that ridge, compared with the effects of other 

 rivers, (for instance, the Rhine below the lake of Constance 

 with a tenth part of the water has worn a deeper bed ten 

 times the distance through the high lands composed of hard- 

 er materials) is against the probability oi such a supposition; 



