290 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
and varying sizes. Many of the columns are 
triangular. <A fine cross-section of this layer 
is seen on the southwest side of Agate Bay. 
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The above section well illustrates the usual alterna- 
tions, but the layers are not always so thin. The upper- 
most layers, seen farther down the coast, appear to be 
much heavier. This may be seen in the vicinity of 
Castle Danger, Sec. 27, T. 54, R. 9 W., and at the Falls 
of the Gooseberry, section 21 of the same township, where 
the massive beds at times exceed 50 feet in thickness. 
While the Agate Bay Group, throughout its whole 
extent, is so plainly made up of a series of thin layers of 
alternating massive and vesicular material, and while the 
general flat lakeward dip is very evident, there are 
numerous minor irregularities, such as running out of 
individual layers, warping of the layers, and faulting. 
All of these render it very difficult to trace out the sub- 
ordinate succession for any considerable thickness. The 
warping of the layers is very interesting. As one fol- 
lows the lake shore single beds may be seen disappearing 
beneath the lake, and reappearing within a few hundred 
feet, while in some cases the warping is much more vio- 
Jent, the rocks for short distances presenting the appear- 
ance of steeply inclined strata, but soon recovering their 
usual position. The general flat lakeward dip, the slight 
deviation of the general trend of the strata from that of 
the lake coast, the warping just alluded to, and the minor 
irregularities of the coast line all combine to produce 
many peculiar effects in the appearance of the stratifi- 
cation, which at first sight are often puzzling. 
Faults, apparently of small extent,—i. e., under 100 
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