Editorial Comment. 
wm 
— 
range dip in a gentle monocline to the south and have been 
gently folded in a direction transverse to the range, The ore bod- 
ies are mainly located in the synclines of these transverse folds, 
and consequently the long axes of most of these bodies lie 
transverse to the range. The original rock of the iron-bearing 
formation, i. e., the rock from which the ore bodies are de- 
rived, is regarded as having the iron in part as a carbonate and 
_in part as a silicate. This silicate, which occurs in green 
granules and is termed glauconite in the Minnesota reports, is 
here stated to contain no alkalies and thus is not glauconite, but 
a ferrous silicate. The primary basis for the map of the Mesabi 
range (maps of the more important parts of all the districts, 
except the Crystal Falls, accompany the paper) is a_ large 
amount of detailed work done by J. U. Sebenius under the 
direction of W. J. Olcott, superintendent of the Lake Superior 
Consolidated iron mines. 
The last chapter of this paper is a comparison 2) 'm- 
mary, and in it the author takes occasion to speak of the quan- 
tity of iron ore available and gives rules for prospecting for 
iron ore in general and in each of the districts in particular. 
The paper is a valuable summary—a full and not a brief 
summary—of the geology of the most important iron ore dis- 
trict in the world. Its chief theme is the genesis and relations 
of the ore bodies themselves, and as such it will prove of espec 
ial value to those engaged in the exploitation of iron ore in the 
Lake Superior region. Papers of this character, especially 
those monographs on which this paper is based and which are 
accompanied by detailed geological maps, have done more 
than anything else to demonstrate to mining men the impor- 
tance of strictly geological work in relation to mining enter- 
prises. And it is not inappropriate to call attention to the 
facts that the work on which such papers is based is conceived 
and carried forward in the broadest spirit of scientific and 
theoretical (using this term in no disparaging sense) investi- 
gation, that the important economic results came as a direct 
consequence of this spirit, and that results of equal impor- 
tance would in all probability not have been reached had the 
work been conceived and carried forward in a strictly economic 
spirit. U.S... 
