Pleutocene Chanye-s of L<;rrJ. — I)i (i<u'i\ ;59 
As the longer axis of this lake trends in nearl}' the same direction as 
the greatest warping of lake Agassiz, it seems probable that the 
limit for this \vari)ing and at the same time for the ui)heaved area 
lies jnst between lake Agassiz' and lake Dakota or through lake 
Traverse. It is bj- no means certain that the limit for the up- 
lifted region or the isoliase for zero remained at the same place 
when the marine limit in the St. Lawrence valle}' was formed; 
but wi' ma}' assume it for this i)art of the continent, since we 
cannot, at present, expect to get more than a general idea of the 
direction of the isobases and their maximum gradient. To judge 
from the prol)able thickness and direction of the receding ice- 
border, it appears that the formation of the highest or Herman 
beach of lake Agassiz was probald}' antecedent to the geoid sur- 
face which is traced in this paper. Moreover, it is quite j^ossi- 
ble that the ice had not receiled from the St. Lawrence valley 
before lake Agassiz received the northward outflow. Vet to be 
(piite sure of maximum tigures for the gradient. 1 have used the 
measurements of the highest oi' ITerman beach, though they may 
b(! too high. 
As to the probaltle position of the marine limit in the other 
northern portions of the area V(!ry little can be adde(l. Some ex- 
plorers, l)elieving that every kind of drift is deposited in the sea, 
have not paid due attention to the determination of the limit for 
the real marine deposits: others seem to have estimated only the 
hight of l).'ach;>s ac:;identally discovered and theij' most relial^le 
observations are made with a barometer often at a long distance 
from any known levt'l oi' i)ase-barometer. 
From Muri'ay's paper on the glaciation of Newfoundland* it 
seems that marin<' deposits are found on that island at a hight of 
about 2(10 feet. According to l{. Hellt distinct beaches are sei'ii 
at Xaclnak in Labrador at an estimated hight of 1,500 feet; but 
I have not found mon; i)recise measurements for tiiese tracts. 
Kven if this measureiHcnt should li.' over-estimatt»il, these beaches 
may be among the highest in all the uplifte;! ai'ea. Hut the 
low levels at which marine deposits are I'ound in the i-elatively 
weil-ex[)loreil soutliei'ii and westei'H pai'ts of ( i I'eenlaiid. make it 
improl)able that the extraordinary high levels, reported as ocrcur- 
"•M'roe. and Trans., (Joy. Soc. ("an., ISS.S. i. pp. ."M-Tli. 
•M;e|)t. (feol. Surv. Can.. 188"j, p. S DD : and Hull. (le,,!. Sacieiy of 
America. I SSn. vol. i. j). 3it8. 
