Reviews of the Ice Aye. 223 
are on the south side of the divide, but nearly up to its summit 
at an elevation of about 1,600 feet above tide. The inference is, 
therefore, inevitable that most of the highest land in northern 
Minnesota was submerged in the Cretaceous ocean and cov- 
ered by its sediments. Attention is called to the fact that 
these recent sediments rest upon the very ancient Taconio 
(Upper Huronian?) or upon the most ancient Archaean. No 
Silurian, Carboniferous or Devonian strata intervene, and it 
is doubtful if they were ever present. During all the ages 
between the primordial and the age of reptiles the rocks of 
northern Minnesota were raised above the waters, dry land, 
subjected to the forces of erosion and chemical disintegration. 
This fact has considerable bearing on the question of the 
genesis of the Mesabi iron ores, and tends to confirm tin- 
theory advanced by the writer in another place.* 
The area at present occupied by Cretaceous is unknown, the 
mantle of glacial drift covering the underlying rocks to the 
depth of one hundred feet or more a few miles south of the 
Mesabi range. There is in St. Louis county an extensive 
swamp occupying a flat tract of land running for nearly fifty 
miles in an east-west direction between the Duluth and Iron 
Range railroad and the Mississippi river. The discovery of 
Cretaceous sediments on the northern edge of this basin sug- 
gests the possibility of a considerable thickness of the same 
sediments in its central portion. From what is known of the 
geology of the area north of the Mesabi range it is safe to 
assert that the most promising field for the discovery of work- 
able brown coal deposits in Minnesota is under this same 
great swamp. 
REVIEWS OF THE ICE AGE AT THE WORLD'S 
CONGRESS ON GEOLOGY. 
Eight papers relating to the Glacial period were presented 
to the World's Congress on Geology in its session on Saturday. 
August 24th, as follows : 
Glacial Succession in thp British Isles and northern Europe. Prof. 
James Geikie, Geological Survey of Scotland. (Absent; read by Prof. 
R. D. Salisbury.) 
^Twentieth Annual Report, Minn. Geol. Survey. 
