Rcr^icw of Recent Ceolofi^ical Literature. 327 
inr.e and long in life, with great erosive power. Perliaps they not only 
(Icnnded the Archcan rocks at Littl-j Falls, hut cut these down to the 
terraces under 500 feet. Then the Iromohawk used the remaining 
drift in the valley as an ahrasive to rasp down the rock barrier to near 
its present condition, cutting away the valley deposits of the earlier 
stage and grading its channel to the falling outlet." 
The ,tinie occupied in the retreat of the ice-sheet from the south 
to the north side of the Adirondack mountains, until it permitted lake 
Iroquois to be drawn down below its Rome outlet, seems to the re- 
viewer to have been probably shorter than it is estimated by the author ; 
for the whole duration of lake Agassiz, th.c largest of our glacial lakes 
and far the longest from south to north, appears to have been no more 
than about one thousand years. 
Furthermore, the time required for the erosion of the gorge below 
Niagara falls, comprising both the Iromohawk stage and the Post- 
glacial stage of the present Mohawk river, is shown by the investiga- 
tions of Wright and the present reviewer to have been probably no 
more than 10,000 or eve;: 7,000 years ; as likewise the age of the gorge 
below St. Anthony falls on the Mississippi, from Fort Snelling to 
Minneapolis, eroded during practically the same period as the Niagara 
gorge, is estimated by Winchell to have been about 8,000 years. In 
that period, the part belonging to the Iromohawk river, that is, to the 
life of the glacial lake Iroquois, could be only a quarter or a fifth, or 
less, leaving: much the greater part of the period as the time since 
tlfe front of the ice-sheet retreated beyond our northern international 
boundarv. \\. v. 
MONTHLY AUTHOR'S CATALOGUE 
OF AMERICAN GEOLOGICAL LITERATURE 
ARRANGED ALPHABETICALLY. 
ADAMS, GEO. I. (A. H. PURDUE and E. F, BURCHARD). 
Zinc and lead deposits of northern Arkansas. U. S. G. S.. Prof. 
Pap. 24, pp. 118, pis. 27, 1904. 
BECKER, GEO. F. 
Experiments on schistosity and slaty cleavage. Bull. 241. U. S. 
G. S., 1904. 
BERRY, E. W. 
The Cretaceous e.xposure near Cliffwood, N. J. (.\m. Geol.. vol. 
34, pp. 253-261, Oct., 1904.) 
BURCHARD. A. H. (G. I. ADAMS and A. H PURDUE). 
Zinc and lead deposits of northern Arkansa.s. U. S. G. S., Prof. 
Pap. 24, pp. 118, pis. 27, 1904. 
