Review of Recent Geological Literature. 251 
courses of drainage adjoining the border of the receding continental 
glacier, whereby the former vast lake Warren was succeeded by the 
Niagara river and falls and by lake Iroquois. While the southern side 
of the old stream channels was the land slope rising from the Ontario 
basin, the northern side in numerous places and for long distances was 
the front of the departing ice-sheet. These latest outflows from the 
lakes held by the ice barrier farther west passed to the Mohawk valley 
and the lake Hudson-Champlain by courses only slightly higher than the 
ensuing lake Iroquois, which outflowed into the Mohawk river across 
the col at Rome, N. Y., the lowest between the highlands of southern 
New York and the Adirondack mountains. The maps and views here 
presented bring most vividly before us a part of the grand changing 
scenes of the closing stage of the Glacial period. w. u. 
The Mesabi Iron-bearing District of Minnesota. C. B. Leith, U. S. 
Geol. Sur., Mon., vol. 43, pp. 316, pis. 33, map, Washington, 1903. 
This valuable and highly interesting memoir, the fourth of the series 
on the lake Superior iron districts by the United States Geological Sur- 
vey, has been awaited with lively anticipation. Being the pronouncement 
of the chief authority on one of the most important geologic provinces 
of the United States, the conclusions at which the author has arrived 
carry with themselves great influence and will have a wide and favor- 
able reception. 
The author treats the Mesabi district in a thorough manner. He goes 
into some detail in the subdivisions of the formations, following, for the 
general nomenclature the terminology which has been applied by the 
U. S. survey to the lake Superior region in general, and applying local 
new terms to the subdivisions. These subdivisions, though previously 
known and noted, had not been specially named. The excellent map of 
the Mesabi district which accompanies the volume indicates the attentive 
and detailed care with which the boundaries of the formations have been 
traced out; and still more detailed maps, both topographical and geolog- 
ical, are presented of certain localities where greater economic interests 
are involved. 
After a synoptic statement of early exploration, of earlier literature, 
of the discovery of the ore and of the recent great economic develop- 
ment, the volume enters upon the actual geology, describing in succes- 
sion the Archean, the Lower Huronian, the Upper Huronian, the Ke- 
weenawan, the Cretaceous and the Pleistocene. The term Archean is 
restricted to the Lower Keewatin, and the Upper Keewatin is termed 
Lower Huronian, while the Animikie, or iron-bearing rocks, is clas>ed 
as Upper Huronian. This criss-cross 'of nomenclature is justifiable, 
perhaps, from the inflexible standpoint of consistency of the U. S. Geol. 
Survey, since this nomenclature has been applied to the same formations 
on the south side of lake Superior, hut it breeds confusion on the north 
side where the Canadian and Minnesota surveys have long used these 
terms in other senses. The description of the "Archean" makes it essential- 
ly an igneous formation, largely composed of greenstone The Lower 
