GLACIAL LAKE WHITTLESEY. 385 



its most distinct correlative, the Alden moraine in western New York, seems to be of minor rank. 

 The Port Huron is a bulky, compound moraine made up of several ridges piled together, whereas 

 the Alden ridge is single and slender, quite like one of the component ridges of the Port Huron 

 system. Such a correlation raises some interesting questions as to the different characters of 

 movements of the ice front at the same time at widely separated places. The Alden ridge is 

 in all probability the correlative of one of the later component ridges of the Port Huron system 

 on the "thumb" in Michigan. 



The manner of the modification of the Arkona beaches, in Michigan especially, suggests a 

 rapid rise of the lake at first with slower rise toward the climax or highest level. This accords 

 well with the supposition that the front stood at least 25 miles back of the Port Huron moramic 

 system during Lake Arkona. It would seem certain that the beginning of a movement of 

 readvance after a backstep halt would be slow at first and would become most rapid in the 

 middle part of the advancing movement, slackening again toward the forward climax. From 

 these theoretical considerations, which are based on the periodic, oscillatory nature of the 

 movements, it is not surprising to find that the beginning of the readvance to the Port Huron 

 moramic system did not affect the level of Lake Arkona but only made narrower the strait that 

 led past the end of the "thumb" to Lake Saginaw. It was only when the movement of readvance 

 was going forward at its most rapid rate and had covered perhaps more than half of its whole 

 interval that it suddenly closed the strait, and the waters east of the "thumb" began to rise 

 to higher levels. Toward the climax of readvance the rate of forward movement became slow, 

 and the last few feet of rise was gradual. The facts seem to bear out fully this interpretation 

 of the manner, rate, and amount of readvance. The recession of the waters must have been 

 still more rapid, for if the glacial oscillations were periodic and superposed on a general move- 

 ment of retreat the backsteps were always longer than the foresteps in distance, though equal 

 in time. Hence, in the oscillations the maximum rate of recession was always inclined to be 

 more rapid than the maximum rate of readvance. 



CORRELATIVES OF LAKE WHITTLESEY. 



During the time of Lake Whittlesey Lake Saginaw was an independent lake (see p. 359), 

 and after receiving theoverflow of Lake Whittlesey it discharged into Lake Chicago, which had 

 then attained hardly half its greatest extent. Two small narrow lakes probably stood in front 

 of the Green Bay ice lobe, but according to Mr. Leverett there was still free drainage and no 

 lakes at the west end of the Lake Superior basin. In New York Fairchild finds Lake New- 

 berry to be the correlative of Lake Whittlesey, but Lake Newberry discharged southward to 

 Susquehanna River. A river of some size entered Lake Whittlesey northeast of Alden, N. Y., 

 and built a delta which buried the Arkona beaches. 



TRANSITORY LATER LAKE ARKONA. 



In falling from the level of Lake Whittlesey to that of Lake Wayne the water level necessa- 

 rily passed the planes at which it had stood in making the Arkona beaches, and Lake Arkona 

 was temporarily revived. But this relation was transitory and endured for so short a time 

 that no evidence of renewed wave work has been found. 

 34407°— 15 25 



