Review of Recent Geological Literature. 373 
and Ely are purer than any ores mined to any extent in the world." 
This is based upon the fact that one-half the ore mined is low in phos- 
phorus, and nearly one-half contains over 65 p. c. metallic iron and less 
than 0.06 p. c. phosphorus. The other half is not quite up to Bessemer 
standard, but its grades are guaranteed to run as follows : Vermilion, 
66.66 p. c, Soudan, 65. p. c. and Red Lake, 62. p. c. metallic iron. 
This is a great showing taking into consideration the high authority 
which is responsible for it. 
In the consideration by the authors of the origin of the Keewatin 
ores (p. 105), there is a contradiction of the conditions supposed by Dr. 
Hensoldt in explaining the deposition of the ores (p. 75). In the latter 
he speaks of the heated waters of an ocean heavily charged with hydro- 
chloric, sulphuric, and other acids, whereas the authors in the first 
citation supposed the volcanic outburst to come in contact with heated 
"aZftali?ie" waters. 
In the explanation (p. 110) of the abundance of iron and silica the 
authors say "these two minerals would have been the first to free them- 
selves from solution and appear as precipitates on the bottom of the 
sea." This does not, however, explain why such a base and such an acid 
should not, in the poetic language of the previous page, have each taken 
the partnerless other and descended to the bottom so conjugated that 
their exploitation as silicate of iron would not to-day be a remunerative 
enterprise. If it is answered that the form of iron which was ejected 
by the submarine volcano was Fe. (Fe 2). Still a little less than 25 
p. c. of all the iron thus released would be like the silicic acid in the 
nascent state and in the most favorable condition to combine. Yet there 
is no record of any large percentage of iron silicate among these deposits. 
A similar origin is supposed for the Taconic as for the Keewatin ores. 
In the synoptical review the presence of titanium is taken in the ores 
of the Vermilion series to indicate an early eruptive origin of the ore, 
and the Vermilion itself as upper Laurentian. The Keewatin ores are 
the chronologic equivalent of the ores of the Laurentian gneises of the 
eastern border. The Taconic (Huronian) ores consist of non-titanic 
magnetites at the bottom, jaspilitic hematites next above, soft hema- 
tites, and titanic magnetites. The Cretaceous limonites are unimportant 
in Minnesota. 
The careful compendium of views on the origin of iron ores does great 
credit to the industry and conscientiousness of the authors. Few sub- 
jects have ever received such a thorough treatment. Besides a classili- 
cation of eighteen theories of the origin of iron ores and a tabular 
statement of the geologists who have favored each theory, there is at 
the end a digest of the views of geologists from the earliest times in 
alphabetical order, occupying 72 pages and containing all of importance 
that has been written on the subject. 
Appendix B is a reprint of a paper read before the Geological Society 
of America on the Taconic Iron ores of Minnesota and western New 
England. Appendix C is a recent paper by the state ereologisl of 
Minnesota before the Minnesota Academy of Natural Sciences. 
