464 



PROCEEDINGS OP BALTIMORE MEETING. 



Comparison of Elevations 





Present alti- 

 tude above 

 tide. 



Former alti- 

 tude above 

 tide. 



Change in 

 altitude. 



Lake Ontario 



Feet. 

 247 

 378 

 440 

 440 

 590 

 860 

 900 



Feet. 



Feet. 



Cayiio'E lake . 







Seneca lake 







Rome outlet of lake Iroquois 



Chicago outlet of lake Warren 



Beach at Crittenden, New York 



Horseheads channel 



50-100 

 590 + 

 590 



(?) 



340-390 



270± 

 (?) 





Difference in 

 nliitude. 



Between Horseheads and Chicago channels 310 feet. 



Between Crittenden beach and earliest and lowest Iroquois beach 635 " 



From this Mr Upham deducts 100 feet as allowance for progressing 

 uplift, giving as an estimate of fall in water surface between lakes 



Warren and Iroquois 535 ' ' 



Differentials of Elevations. 



Crittenden beach, from Toledo, Ohio, to Crittenden, New York, 9 inches per mile, 



east-northeast. 

 Iroquois beach, from meridian of Crittenden to meridian of Rochester, 9 inches 



per mile, east. 

 Iroquois beach, from Rochester to Rome, practically level, east and west. 

 Iroquois plane, from Weedsport to Richland, 3 feet per mile, northeast by north. 



Most of the glacialists who are working upon the extinct lakes are of opinion 

 that the earliest Iroquois beaches were formed not far above sealevel. AVith no 

 north-and-south differential elevation, the Horseheads col would then be carried 

 far under the Chicago outlet, but there is evidently considerable north-and-south 

 differential in the region immediately north of the Finger lakes ; consequently 

 just here is the real quantitative problem, which cannot be solved until much care- 

 ful work has been done upon the shore phenomena of the glacial Watkins and 

 Ithaca lakes. 



Mr Gilbert thinks that the earliest Iroquois plane passes beneath the surface of 

 Cayuga lake not farther south than the middle of the lake, and with an inclina- 

 tion of perhaps 3 feet per mile. Assuming the subsidence from the Warren level 

 to the Iroquois level as 53'> feet, then 378 feet, the present altitude of the Iroquois 

 plane where it cuts the surface of Cayuga lake, would have been in early Iroquois 

 time 323 feet lower (378 — (590--535) — 323), but Horseheads is 35 miles farther 

 south, and continuing the Iroquois plane with the same inclination would allow 

 the Horseheads channel a depression of only 218 feet. A depression of 310 feet was 

 necessary to make it drain the Warren waters. 



The above calculation illustrates the negative argument ; but even if that result 

 be established, it will not be conclusive. The episode of lake IroquoiSj with the alti- 



