Tlie Second Lake Al(/o)iqiii)i. — Ttn/lor. 165 
ward elevation was required to cause the change oi' outlet.* 
From a consideration of the plane as above, we may argue 
that, since the Nipissing beach south of the North Hay axis 
was formed when both outlets were active at once, and since 
there is no extra rise of the plane north of that axis, it fol- 
lows that all the lower beaches of lake Algonquin have been 
made since the St. (ylair outlet opened. That being the case, 
it follows that very nearly all of the deformation which has 
affected the Nipissing plane must have taken place after the 
abandonment of the North Bay outlet. And further, since 
the last 40 feet of elevation at North Bay did not carry the 
water plane up with it, we may be sure that the St. Clair out- 
let was active at the time it occurred. These facts indicate 
that the level of the sea in the Mattawa and Ottawa valleys 
east of North Bay had probably fallen only a few feet below 
the level of lake Algonquin before the outlet was changed and 
the outflow at North Bay ceased. This agrees witli the re- 
ported fact that the lower valley of the Mattawa shows no 
certain evidence of having been recently occupied by a great 
river.f 
While these considerations do not locate the main eastward 
uplift exactly in time, the character of the beaches, however, 
seem to show that none occurred until after a simple north- 
ward rise of at least 25 or 30 feet had taken place on the south 
Superior shore. But there is good evitlence to show that the 
simple northward rise was considerably nu)re than this. The 
Pictured rocks. Grand and Au Train islands aiul the north 
end of Presque Isle are sheer clitl's, standing with their bases 
submerged. The}' show that no eastward component of ele- 
vation att'ected lake Superior until a considerable time after 
*It is possible that a (•oiisidei-abic part of the time of lHi<e i\l,n()ni]uiii 
l)asse(l before the time of tlie Nipissint;- beacii. That ])erio(l may liave 
been closed by an nplifl at North Jiay raisinii' the water in liie whoh' 
basin to the level of the Nipissiiii;- beach which then lienan lo lir formed. 
Jint if there was such an nplift it was probably slight, ami no certain 
evidenci' of it has yet been fonnd. 
fin his i>aper referred to aixive. Prof. Wright di'scrilies a great i)onl- 
der terrace SO feel above the river al Mattawa, and altribules it lo the 
action of the old ontiet river. Il seems probal)le. howexcr, thai Dr. 
Bell is right in supposing this parllcnlar terrace to l)e morainic. Il iloes 
not appear that the declivity of liie Mattawa immediately above the 
N'illage is snMicieiitly steep to account fni' such an accnninlal ion as the 
result of river action. 
