ProUems of Mesahi Iron Ore. — Winchell. 169 
This illustrates the general law of the close relationship between 
the fossil faunas and their environment. 
Just as the geologist knows how to interpret the fineness or 
coarseness of sediments into relative distances from a shore line, 
so the paleontologist is able to see in the shifting of faunas and 
the comparison of species evidences of elevation or depression of 
the marine bottom, which upon reaching sea level produced often 
the diversion of ocean currents and consequent modification of 
faunas. By the comparison of extinct faunas he learns to recog- 
nize the continuity or the discontinuitj" of the conditions of en- 
vironment such as mark geographical areas of distribution of 
living animals. The fossil faunas, their modifications and their 
migrations, as indicated Ijy presence, absence, rarity, abundance, 
size, variation, or mutation of their species, are the sensitive evi- 
dences of changing geological conditions upon which the geolo- 
gist must depend for tying together his disconnected facts. 
Fossils have too often been regarded as only marks for distin- 
guishing the different geological formations, but the scope of the 
paleontology of to-day is far wider. The modern conception of 
the evolution of life has made paleontology the science of the 
History of Organisms. And it is because fossils exhibit in mor- 
phological characters the evidence of the ancestry through which 
they have arisen, and of the conditions of environment through 
which they have successfully struggled, that they are of such 
paramount value in all geological investigations in which the ele- 
ments of time or the order of sequence of events is concerned. 
SOME PROBLEMS OF THE MESABI IRON ORE.* 
N. H. Winchell, Minneapolis. 
CONTENTS. 
Theories of the origin of the ore already proposed. 
Some facts of its manner of occurrence. 
Extent of the range. 
Kinds of ore. 
The titanic ores excluded from this discussion. 
Difflcnlties in the way of acceptance of any of the proposed theories. 
Absence of limestone in the iron bearins horizon. 
Diffusion of iron through ferriferous schists rather than concentration. 
Why is such supposed concentration always at the same horizon ? 
Absence of dikes cutting tilted beds. 
Prevalence of pervious rather than impervious strata. 
Evident changes in the rock of the country, whether in the forms of breccia and 
gravel or in situ. 
Some ISecessary Postulates. 
1. The ore has a definite position in the stratification. 
•2. It is underlain by a porous quartzyte. 
*Read, August 22, 1892, before Section E, of the American Association 
for the Advancement of Science, Rochester, N. Y. 
