Ii8 TJie American Geologist. Febmary, issis 
first described under new names, the survey of the high level 
terraces in the mountain regions has suggested to the writer 
counterbalancing evidence of the occurrence of glacial dams, 
but this is a study which has been postponed, partly on ac- 
count of the prejudice against post-glacial subsidence and 
partly on account of the writer's absorption in other ques- 
tions of physical changes. Whatever may be the ultimate 
fate of the theory of glacial dams, the opposing hypotheses 
have given zest to the investigations to the degree of ad- 
vancing our knowledge of the lake history. 
In the survey of the beaches, besides the terrestrial de- 
formation recorded, there seems to be no more important 
discovery than when the writer found how the Huron, Michi- 
gan and Superior waters (the Algonquin gulf or lake) origin- 
ally emptied to the northeastward of the Huron basin in place 
of discharging into lake Erie; after which by the northeastern, 
tilting of the land "the waters were backed southward and 
overflowed into the Erie basin, thus making the Erie outlet of 
the upper lakes to l^e of recent date."* This conclusion was 
established by the survey of the Algonquin beach which re- 
corded the necessary tilting. The first survey was suspended 
near Balsam lake, where an overflow was found; and, accord- 
ingly, in the original announcement, the generalizations were 
not carried farther, although there was a lower depression in 
the vicinity of lake Nipissing, which was shortly afterwards 
made use of by Prof. Gilbertt and the writer. With the 
further elevation of the land, the lower beaches — partly meas- 
ured at that time (1887-8), represented the surface of the Al- 
goncjuin water discharging by the Nipissing route alone. t 
This has since been worked out by Mr. Taylor. § 
Co-existing with the Algonquin gulf or lake was the 
Lundy gulf or lake, occupying part of the Erie basin, and ex- 
tending into the Ontario, having substantially the same level. 
Both of these bodies of water extended much farther towards 
the northeast than their successors, although more contracted 
in the opposite directions — the eflfect of the more recent tilt- 
*Proc. A. A. A. S., vol. XXXVII, 1888, p. 199. 
fThe History of the Nipissing River. 
:j:Deformation of tlie Algonquin Beach, cited before. 
§The Ancient Strait of Nipissing. F. B. Taylor. Bull. Geol. Soc. 
Am., vol V, 1893. 
