GLACIAL AND INTERGLACIAL BEDS 303 



present level of lake Ontario for about five miles, probably by 

 the Laurentian river, which seems to have shifted its bed 

 towards the east as the lake level sank, to avoid the thickest 

 part of the previously formed delta. As no peaty clay has been 

 found in the cuttings made by the Rouge and Highland Creek, 

 but only bowlder clay and later stratified clay and sand, this 

 interglacial valley seems to have been extensive. 



Walking westward from Highland Creek the slope of the old 

 valley is seen to rise gently, first the peaty clay showing above 

 the water and becoming thicker and thicker, and then the 

 overlying sand showing itself, finally reaching its maximum 

 thickness about four miles from the first appearance of the peaty 

 clay on the lake shore. How much of the valley already existed 

 before the river began its work is unknown, but at least a 

 considerable thickness of the tough peaty clay must haVe been 

 cut through, for at Rosebank to the east of the old valley it 

 rises 20 or 30 feet above the lake. 



Continuing westward along the shore a second much nar- 

 rower valley still buried under till and unfossiliferous stratified 

 clay is seen at the " Dutch church," as a vertical promontory 

 three miles from the western end of the Scarboro' section has been 

 called. This " fossil " valley was cut through the full thickness 

 of interglacial sand and clay to a level below the present lake, 

 on the shore of which it shows a width of about 1200 feet. At 

 the top of the peaty clay, 90 feet above the lake, its width 

 is about double this ; and its sides then slope gently up to the 

 top of the stratified sand with a total width not much short of 

 a mile. The Dutch church valley was apparently made by a 

 comparatively small stream. 



It should be mentioned, however, that Professor Albrecht 

 Penck gives another explanation of the downward dip of the 

 bowlder clay at this point, supposing that the promontory is 

 really a mass of till lodged to the south of an old lake cliff of 

 interglacial times. The old cliff has been exposed again on each 

 side of the Dutch church by the action of the present lake, but 

 the tough clay at that point has resisted better and still remains. 



