J. P. Kimball on Iron Ores of Marquette, Michigan. 301 
_ power of resistance in the arch is strikingly illustrated ; for while 
the crest itself remains perfect, the same strata have 
disrupted and displaced as they pass out of the arch and change 
their curvature. e upper laminated portions are exceedingly 
_wrinkled, and the heavy beds broken and doubled. Under these 
areumstances of displacement but one or two of the heavier 
beds of argillite are exhibited above the grade of the railroad; 
ind while these, through scales or plates retain marks of strati- 
fication so as to expose their true character, they have been 
sharply folded and collapsed, and by their nearly vertical posi- 
tion have the appearance of intrusive masses. e central por- 
tion of the cutting—that is, the undisrupted strata—is traverse 
byasystem of parallel joints which the disrupted portions are 
Without. Several segregated veins of quartz with limonite oe- 
_tipy the divisional planes of stratification. 
Be Other sectional cuttings in the several mines or quarries dis- 
_ play more or less completely the stratification and undulations 
ofthe hematites in common with the Huronian scbists of this 
Tegion, and show conclusively, if further testimony were requisite, 
; the existence of the iron ore under the same conditions of de- 
- Post and secondary modification as the schists with which they 
M@associated. In the Jackson mine, for instance, occur two 
Wes or short anticlinal folds, while in the Lake Superior mine 
gaan they contain; but the pebbles of specular peroxyd, 
h sometimes obscure in a matrix of the same material, 
been tates, owing to their enduring composition, have re- 
= — Sunies, Vou. XXXIX, No. 11Z—Mar, 1865, 
