406 Scientific Intelligence. 
the Lake Superior mine. Under a lens this shows a fine contor- 
ted banding. Microscopically this section is composed of a fine 
granular aggregate of quartz and hematite, and a more coarsely 
tite, and of quartz of secondary origin. The quartz in the first 
whie also c occurs in irregular masses and in octahedrons. The 
crystalline form it is in octahedrons. The color and streak o the 
iron in the hand meree are those of hematite, = the powder 
is found to be magnetic. e section was taken from the most 
jaspery portion, and shows much of the fine aggr eqation of quartz 
and hematite. The structure of the quartzose portion is like the 
devitrification structure of the rhyolites and felsites. The section 
as been repeatedly fissured, and the fissures filled in with second- 
fractures filled i Sees manner. e jaspery eg is finely 
banded, ~ phen an apparent fluidal structure. We are 1n- 
a 
pointed out . Wichmann.* The powder of the two last- 
described specimens is feebly magnetic. The quartz is mu uch 
ame ai showing the _ of heat, and contains microlites and 
flui stone inclusio 
The “octahedral bom. “of the iron ore would sustain the view 
the jasper. Our ia rane examination of rocks of various ages 
and characters goes to show that all rocks, especially the older, 
been subject to more or less alteration. This alteration is 
the medium of the percolating waters, and consists rathe 
chemical rearrangement of the constituents of the rock, amongst 
in t 
from extraneous sources, e jasper and iron ores, as well as all 
other rocks examined Piceeeen from this district, have suf- 
fered this alteration to a greater or less extent; therefore it is 
perhaps pastes . present to oe ure of ie original state of 
the iron, or how vhanges have taken plac 
Without objecting in any degree to the 5 that the ore was 
originally magnetic, certain facts indicate that the present mag- 
* Geol. of Wisc., iii, 615. 
