THE CUYAHOGA DELTA. 331 



erosion of rains, rills, larger streams and the Cuyahoga itself in its gradual 

 reexcavation of the valley to keep pace with the declining levels of the 

 lake, or, we may better say, with the progressive elevation of the land. 

 This northern part of the delta covered the earlier driftwood and mainly 

 attained, like the older southern part, a somewhat uniform depth of 10 

 to 20 feet, overlying the till and sloping, like that deposit, from south to 

 north — that is, toward the lake — at a varying rate of 25 to 50 feet per 

 mile. 



The area of the Cuyahoga delta thus described is approximately coex- 

 tensive with the city of Cleveland. It lacks, however, about two miles 

 from reaching to the city limits on the west, being there bounded by a 

 tract of till which is a continuation of the same topographic plain. On 

 the southeast it fails of extending to the city boundary by about one mile, 

 being succeeded by a somewhat rapidly ascending slope of till with rock 

 beneath at no great depth, from Newburg to Kinsman street, beyond 

 which, northeastward, the rising slope of till and rock outside of the delta 

 and within the city limits is narrowed to a third or half of a mile in the 

 vicinity of the Western Reserve University. Thence the delta continues 

 east through Glenville and Collinwood, as extended by the prevailing 

 eastward drift of the old glacial lake currents, which were caused by the 

 winds to run like those of the present lake Erie The maximum width 

 of the delta is about five miles, its length in the cit}^ of Cleveland, par- 

 allel with the lake shore, is eight miles, and its area, so far as it lies wdthin 

 the city, is about 25 square miles. 



Recent undermining of the shore cliff by wave erosion along the dis- 

 tance of nearly a mile from the foot of Willson avenue east to Gordon 

 park exhibits a continuous section of the delta sand, yellowish gray, hori- 

 zontally stratified, 15 to 20 feet thick, separated by a definite level plane 

 from the underlying dark bluish till, which holds abundant gravel and 

 cobbles up to 3 or 4 inches in diameter, and occasionally of twice or three 

 times that size, while larger boulders are absent or exceedingly rare. The 

 cliff has a nearly constant height of 35 feet above the lake, and its lower 

 half consists of this till, which also extends to much greater depth beneath 

 the lake level. Through all the extent of the section the till is more or 

 less clearly laminated from its top down to the shore, and in many places 

 the laminae show much contortion, although mainly they are horizontal. 

 The inclosed stone fragments become more plentiful downward, but the 

 lamination in general becomes less discernible in the same direction. My 

 observations, as thus noted, indicate that the englacial drift here was not 

 less than 15 or 20 feet thick. It was laid down as the laminated till in 

 the water of lake Warren, about 150 feet deep. As no interbedding or 

 blending of the till and the delta sand is anywhere seen, it appears cer- 



