i6z POPULAR SCIENCE MONTHLY. 



to four hundred and fifty feet high, and the whole somewhat fur- 

 ther submerged. Again it passes through the narrows across the 

 broken mountain ridge into Georgian Bay, where the deep chan- 

 nel skirts the foot of another high escarpment. The old water 

 way across these lakes is shown on map (Fig. 5). 



From Georgian Bay the ancient channel is buried below drift 

 deposits to a known depth of seven hundred feet, and almost cer- 

 tainly the drift reaches to a depth of one thousand feet beneath 

 the highest obstructing ridges. The course of the channel passes 

 through Lake Simcoe and enters the Ontario Valley about twenty 

 miles east of Toronto, where the deep trench is made known by 

 the soundings in the lake. The buried valley was broad and 

 comparable to the portions through the lakes. On its western 

 side, but some miles away, it is paralleled by the " mountain " or 

 Niagara escarpment, which reaches to more than fifteen hundred 

 feet above the sea. On the eastern side of the valley the plains 

 are underlaid by solid rock, although these are often covered by 

 drift ridges. Between these rocky boundaries the drift has been 

 penetrated to great depths in many places, yet in the center of 

 the channel the bottom of the filling has never been reached. 



Throughout the Ontario Valley the Laurentian River flowed 

 at the foot of a high escarpment now submerged (see Figs. 3, 5, 

 11). At the eastern end of Lake Ontario the channel turned 

 toward the present outlet of the lake and then down what is now 

 the modern course of the St. Lawrence to the sea. The origin of 

 the barrier across the present outlet of Lake Ontario will be no- 

 ticed later. 



One of the great tributaries was the Huronian River, crossing 

 the southern portion of Michigan, as shown upon the map (Fig. 

 5), and extending through Saginaw Bay to join the Laurentian 

 River farther north. The Superior outlet is supposed to have 

 crossed the upper peninsula of Michigan and joined the branch 

 draining from the northern end of what is now Lake Michigan. 



The now shallow Erie basin was then a portion of a plain 

 across which the ancient Erigan River flowed in a valley two 

 hundred feet or more in depth. One of the buried and submerged 

 tributaries at Cleveland was described by Dr. J. S. Newberry, 

 others by Dr. T. Sterry Hunt, and those near Buffalo by Dr. J. 

 Pohlman. From the Erie basin the Erigan River crossed by a 

 channel about forty miles west of the Niagara River, which did 

 not then exist, and passed down the Dundas Valley (Fig. 4) into the 

 head of the Ontario basin, and farther eastward joined the Lauren- 

 tian River (Fig. 5). All the features of the ancient and drowned 

 valleys are those characterizing ancient topography; that is to 

 say, without the boldnesses and abruptnesses of youthful features 

 and without great waterfalls, although rapids must have existed. 



