1()4 'rtiC Anicricdll (ieahxjisl. Marcli, 1895 
lake Al^oiKiuiii conic iiiti) existence. Tliere probably was 
Bome elevation at its outlet in the earlier days of lake Algon- 
quin, lint it is almost certain that there was none, or at least 
exceedingly little, in its closing days. For, as was pointed 
out above, an elevation of the outlet would cause all the shores 
of the lake to be submerged. The character of the beaches 
on the Superior shore, however, shows very clearly that no 
such change occurred during, nor for a long time after, the 
formation of the Ni]iissing beach and that at least in its later 
days the shores of lake AlgoiKiuin were not disturbed by any 
noticeable eastward deforjnation. But the Nipissing beach 
rises eastward and there is the old outlet to-day 160 feet 
above lake Huron and 40 feet above the main Nipissing plane. 
The only exi)lanation which is entirely consonant with all the 
facts requires us to suppose that the eastward factor of de- 
formation began at some time after the North Bay outlet, and 
the whole Ni[)issing beach, with all those for :^5 feet or more 
below it, had been abandoned and left high and dry in conse- 
quence of simple northward differential elevation. And this 
northwai'd elevation must have been very gradual and very 
uniform in its rate, if the present appearance of the Superior 
beaches goes for anything. On this line of evidence I am 
driven to conclude that it was not an eastward elevation that 
caused the change of outlet but a northward one. This points 
in turn to the more impoi-tant conclusion that lake Algonquin, 
as defined by the Nipissing beach, was probabl}^ in a geolog- 
ical sense a very short-lived affair. For if there had been 
mu(-h northward differential elevation while the North Bay 
outlet was active and without causing it to go dry, the plane 
of lake Algonquin would have changed its attitude by swing- 
ing on an east-west axis through the outlet. The upper aban- 
doned beach of Nipissing age north of that axis would then 
a))pear to rise northward more rapidly than that south of it. 
But no evidence of such a change of plane was found; on the 
contrary there is conclusive proof against it. For the nuiin 
plane of the Nipissing beach passes right across the east-west 
axis apparently without the slightest sign of a break. This 
shows that the level of lake Algonquin from the beginning of 
the Nipissing beach must have been very close to the level of 
the St. Clair outlet ; so close that only a very slight north- 
