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< Geological Structure of Keweenaw Point. 67 
this fact now in order to recall to your minds the objections that 
were made to my views on this subject at our meeting in 
Haven, in 1845. The predictions I then made are now fully 
verified. 
- Nature of the Veins in the Trap rocks.—There are two class- 
es of veins known to miners on Lake Superior, viz.: Ist. Those 
running with the “country,” or parallel to the course of stratified 
rocks through which the trap rocks pass—veins that are sometimes 
-. called beds, or interstratified masses. And 2nd. Those which cross 
the “country,” or cut transversely at various angles the line of di- 
rection of the strata. 
These last are called true veins, and are the only ones on which 
miners have thus far placed reliance as to their continuing rich to 
any considerable depth. [ do not regard the question as fully set- 
tled by experience in this district, that mining should be confined 
to the transverse veins, for there is reason to believe that both 
classes of veins are of the same origin, and no facts have yet 
been adduced to prove that veins running with the “country” 
cannot be advantageously wrought. On the contrary, it is known 
that large quantities of native copper are raised from this class of 
veins on the Ontonagon River, and it is probable that some on 
Isle Royale will ultimately prove valnable. A few good practi- 
cal experiments in mining will settle this mooted point in practi- 
eal geology. It is obvious, since the trap rocks are not reall 
stratified, that this class of veins cannot be correctly denominated 
interstratified, though they may be imbedded. 
The first class of veins run, as will be understood by what I 
have previously said, nearly E.N.E., W.S.W., varying with the 
flexures of the line of junction of the trap and sandstone, and are 
included between the two rocks in amygdaloid or in epidote, this 
mineral being the most usual gangue or matrix of the copper. 
Regular walls of solid copper of some inches in thickness, have 
en observed in one of the new mines opened in the Ontonagon 
River, and sheets of considerable size have been found in the 
east and west veins on Isle Royale. 
Mining operations are now in progress to test the permanency 
of these veins; we shall know in a year or two the results. 
The second class or tranverse veins run generally in a course 
N. 26° to 30° W., S. 26° to 30° E., and consequently cut across 
the line of direction of the trap rocks and adjacent strata, They 
rap. 
following species of minerals: prehnite, calc spar, laumonite, 
dite, quartz, datholite, chabasite, mesotype, apophyllite, 
, analcime, and wollastonite. 
