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Copper and Silver of Kewenaw Point, Lake Superior. 83 
_ After a pleasant journey and voyage from Boston to Mackinaw, 
we took a boat for the Sault St. Marie, and made a trip of about 
ninety miles from Mackinaw to the Sault, encamping two nights 
on the islands on our route, and reaching Lake Superior on the 
evening of the third day. Most of the islands which we passed 
were composed of compact white limestone, containing a few fos- 
sils, and apparently of the same age as the Niagara limestone of 
New York, and like it containing occasionally a little gypsum. 
On reaching the Sault, the character of the rocks is altogether 
changed, and red and grey sandstone, which, according to Dr. 
Houghton, is of the old red series and destitute of fossils, is ob- 
served, and forms the falls or rapids by discharging the waters of 
Lake Superior over the outcropping edges of their strata. The 
sandstone: dips towards the lake, and the waters, passing up 
their gently inclined surface, fall in foaming rapids from the up- 
per edges of the strata; while along the whole upper side of this 
slope, myriads of large rounded blocks of primary and trappean 
rocks have been deposited by the sheets of ice, which must have 
transported them from a great distance—no such rocks being 
found in place near the outlet of the lake. These bowlders were 
probably brought by the ice, or streams coming from the moun- 
tains, to the lake shore, and from thence ice-rafts have transported 
them to their present resting places. They abound not only in 
the rapids, but also on the more elevated land around the falls, 
and indicate the ancient level of the waters of the lake to have 
been much higher than it has been during the historical epoch. 
The geologist will observe among these rounded blocks of stone, 
representatives of all the different rocks of the lake coast and of 
the country traversed by its tributary streams. Those which 
are most remarkable are syenite—often mixed with epidote, a 
mineral not unfrequently mistaken for copper ore—red porphyry, 
quartz rock, greenstone trap, conglomerate and red sandstone. 
The rock in place beneath this covering of bowlders, as before 
observed, consists of strata of mixed red and gray sandstone, 
which is covered with only a few feet of sandy soil, and is fully 
exposed along the line of alittle canal made for a now abandoned 
saw mill. This canal extends from the lake to below the falls, 
and is nearly amile in length. The fall from the level of the lake 
to the river St. Mary below the falls, is from eighteen to twenty 
feet, according to the measurements which I made at the termi-: 
