J.P. Kimball on Iron Ores of Marquette, Michigan. 303 
it uent 
ecial instances it may have been derived y hag a 
version of greenstones into schalstones, or ry 
i ian 
be—as shown by Bischof™ in promonneing. te ti pd pide 
atacters of these rocks. Froma stratigraphical po 
and m 
‘Untenable, it is 
Y portion of th 
Bischo i d District, ii, 17, 93. : 
» Report the Lake Superior Lan eget" % 
po pene Persad and Physical enh 10 mig sane Ltn, 
85. Volger, Studien zur Entwicklungsgeschichte 
