Tlie Second Lake Al(/oiiqi!iii. — 'T<n/lor. Ill 
rapidly to the northeast is, therefore, a thing of different age.* 
In the case of the Nipissing beach the value of the suppo- 
sition of its extension, as above, to the southern shore of lalie 
Huron is strengthened by the fact that although it has been 
traced to widely separated points elsewhere, this beach is 
not known to depart suddenly or greatly from its mean plane. 
The only notable exception to this statement is the acceler- 
ated rise northeastward toward the North Bay outlet in the 
region northeast of lake Huron. But at North Bay the alti- 
tude of the beach above the main plane produced to that place 
from the west is only about 40 feet. 
The Change of the Outlet and the Deformathjn of the 
NiPissiNG Plane. 
Theorefical Considerations. We have now before us a re- 
sume of the principal facts relating to the Nipissing beach of 
lake Algonquin so far as at present known, and upon these as 
a basis we must endeavor to learn what we can of the history 
of that lake and the proximate causes of the changes whic'h 
led to its deformation. But first a brief consideration of cer- 
tain theoretical principles will help us to understand the na- 
ture of the changes which have taken place. 
If a basin which receives a continuous supply of water and 
maintains a continuous outflow be tilted in any direction, its 
relation to the plane of the water surface will be changed. If 
the outlet were on the east side and the basin were tilted up 
at that side, all the previous shores in the basin would be sub- 
merged. On the other hand, if the west side were elevated 
the previous shores would all be left drJ^ If the basin were 
tilted up at its south side only, the water would change its 
level on an axis running west from the outlet and all previous 
shores south of that line would be left dry, while all north of 
it would be submerged. On the other hand, if the north side 
were elevated the new relations would be just the reverse; 
previous northern shores would be left dry and southern ones 
*ln some of his rt'ccnt pjipcrs Mr. Warren U))ham has endeavored lo 
show that the Nipissinj"- beach is the same as Dr. Spencer's AljioiKiiiin 
beach. (See pp. 21-27, Hull. G. S. A., Vol. vi, 18114: pp. .'i^Ot), Geol. and 
Nat. Hist. Survey of Minn.. Part 111, 1804: and Am. .lour. Sci., Vol. 
XLix, .Ian. 18!).').) 1 have observed botii beaclies at tliesame locality. 
The two are entirely distinct and independent, tiie Al«?on(piin always 
occurrinj:' above tlie Xipissinj,' so far as yet seen. 
