Review of Recent Geological Literature. 253 
relating to the features of the ore deposits themselves, and to the origin 
■of the ore masses. Accepting the conclusions of the Minnesota survey 
as to the primal source of the ore, so far as it can now.be actually traced, 
namely a green sand whose disintegration has given rise to the two chief 
elements in the ore, (hematite and quartz) he nevertheless fails utterly 
to give any positive explanation of the, origin of this sand, though some 
halting hypotheses are offered supported by some assumptions. This 
sand was supposed by Spnrr to be of the nature and origin of glauconite, 
and by Winchell to be more or less altered obsidian sand. Nothing can 
be considered demonstrated as yet to the satisfaction of geologists as to 
the origin of this "ferrous silicate," and it will probably remain for some 
years one of the unsolved problems of the lake Superior iron ores. The 
following quotation expresses the author's belief : 
"The iron ore was carried to the Upper Huronian ocean in solution, 
probably as carbonate, was precipitated as ferric hydrate, was buried 
with the vegetable material and reduced to the protoxide form, and was 
then combined with silica to form ferrous silicate. In the Gogebic dis- 
trict where silica was not present in so great abundance, the protoxide 
combined for the most part with carbon dioxide to form iron carbon- 
ate. The shapes of the granules may be due to replacement of minute 
shells, such as those depositing glauconite, or those giving shape to the 
granules of much of the Clinton ore." 
That is a pretty long and complicated cycle of hypothetical chemistry, 
involving hypothetical physical changes. 
Mr. Leith names this greensand greenalite, 
Two chapters are devoted to matters of immediate economic interest, 
such as distribution, transportation, production, reserve, ownership, 
prices, methods of mining, and guides to future exploration. All in all 
the book is a welcome addition to the literature of the lake Superior 
ores. n. h. w. 
Kansas Glaciation and its Effects on the River System of Northern 
Pennsylvania. By Edward H. Williams, Jr. Proceedings of the 
Wyoming Historical and Geological Society, vol. VII, 1902, pp. 21- 
28, with six plates. 
The oldest till in north central Pennsylvania overlies the eroded and 
smoothly planed outcrops of coal beds, which have been scarcely affected 
by chemical changes due to infiltration of water through the porous till, 
indicating that no very long period has elapsed since that earliest rec- 
ognized stage of glaciation. 
Professor Williams here maps a glacial lake that occupied the val- 
leys of Bald Eagle creek and the West branch of the Susquehanna from 
near Tyrone northeast to Williamsport, having a length of about seven- 
ty miles and a width varying from one to five or six miles, with several 
large bays in the mountain valleys on either side. It is named lake Les- 
ley, in honor of the late J. Peter Lesley, who directed the Second Geo- 
logical Survey of Pennsylvania. 
