192 THE CANADIAN NATURALIST. [Vol. viii. 



The establishment of this conclusion is however only the 

 first step. If it is proved that the Erie valley existed not as a 

 lake but as a valley at the time in question, other changes must 

 follow. We quote again from the Survey of Ohio : 



" An old excavated and now filled channel connects the basins 

 of Lake Huron and Lake Erie. At Detroit the rock surface is 

 130 feet below the city. In the oil regions of Enniskillen and 

 Bothwell, on the opposite side of Detroit river, from 50 to 200 

 feet of clay overlie the rock where the land surface is but little 

 above the level of Lake Huron. The greatest depth of this 

 channel is unknown." 



The existence of this old and buried chanel at Detroit is an- 

 other link in the chain. It enables us to extend our inferences 

 from the valley of Erie to the basin of Lake Huron. It is evi- 

 dent that if the former in pre-glacial times contained no lake, 

 and was connected with the latter by this channel 200 feet in 

 depth, now filled with drift, the latter must also have been an 

 open valley, and not, as now, the bed of an inland sea. The 

 water collected upon its slopes must have flowed down to the 

 mid-channel and thence through the deep gorge at Detroit into 

 the Erie valley, forming the river previously mentioned.* 



Turning now to the other end of Lake Erie, let us consider 

 the physical condition of the Ontarian valley at the time in 

 question. The greatest depth of Lake Ontario is 450 feet, with 

 a surface level of 235 feet above the sea. Between the two 

 lakes lie, as is well known, the falls of Niagara, which with the 

 rapids below and above them, cause a descent ot 330 feet. We 

 have shown above that the valley of Erie cannot have been in 

 early Quaternary times the bed of a lake, and it is therefore 

 necessary to find some means of accounting for the escape of the 



* It may be well in this connection to mention that the often 

 expressed conception of these lakes as profound depressions is quite 

 incorrect. They are excavations insignificant in depth when we 

 consider their area. Lake Erie, with an average breadth of about 

 40 miles and a depth of 200 feet, lies on a bed whose sides slope only 

 10 feet in a mile. To the eye such a slope would appear an absolute 

 level, and when we consider that a railway incline sometimes rises as 

 much as 80 feet in a mile, the flatness of this valley to the eye will 

 bej more apparent. A similar calculation applied to Lake Huron 

 shows that its bed slopes on an average not more than 16 feet in the 

 mile, and like results mav be obtained for all the others in the chain 



