606 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



summit in tlie valley west of Akron, as shown by the survey of the Northern 

 Ohio Railroad, stands 425 to 435 feet above Lake Erie, while the summit 

 along the Ohio Canal is 396 feet. In the northern portion of the Cuyahoga 

 Valley the upper limit of the silt decreases to 200 feet or less at the borders 

 of the old lake terraces. 



In the other valleys tributary to Lake Erie the silt deposits which 

 have been observed beneath the till have the compact texture and nearly 

 entire freedom from pebbles of those in the northern portion of the Cu3'-a- 

 hoga Valley, and, like tliem, contain a large amount of lime, as shown by 

 nodules and by effervescence with hydrochloric acid. In the valley of 

 Chippewa Creek and River Styx, which lead southward into the Tusca- 

 rawas, the silt deposits are known only by records of wells bored in them, 

 and the writer had no opportunity to see specimens from these wells. The 

 streams which lead northward from the continental divide are more rapid 

 than those leading southward, and consequently have deepened their valleys 

 sufficiently to expose nearly the whole section down to the rock floor. 



It is not improbable that silt deposits similar to those exposed along 

 these northward-flowing streams occur also beneath considerable portions of 

 the low interfluvial districts of northern Ohio, whose altitude is but little 

 above the streams, as is the case between the tributaries of Black River and 

 between Black and Rocky rivers, but no exposures were observed in that 

 district which reached the bottom of the till. In the hilly districts from 

 Rocky River eastward the silts are ajDparently confined to the valleys. 



The age of these silts and the conditions under which they were 

 deposited afford material for much study and speculation. The silts may 

 represent several distinct depositions at intervals widely separated, though 

 no evidence was found to support this conception, the heavy deposits on 

 the Cuyahoga presenting, so far as examined, no unconformable beds and 

 no alternations of oxidized and unoxidized silts. The silts were probably 

 deposited, as suggested by Claypole, in bodies of water outside the ice 

 sheet, the ice sheet acting as a barrier to prevent northward drainage of the 

 water, though it is possible that in some cases they are the deposits of sub- 

 glacial waters. The scarcity of coarse material in these deposits, however, 

 seems to strongly oppose the h5'pothesis of subglacial deposition. The 

 fringing lake may have been formed either during an advance or a retreat, 

 or have embraced both an advance and retreat in cases where the ice failed 



