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and Changes of Level in Lake Superior. >. @ 
the water, were daily observed (except from the 3d to the 8th of 
August ), when the water was calm, and a steady progressive rise 
noticed by means of them, the lowest being first covered and 
others in succession. It has been observed on this lake, that the 
water is lowest in spring and highest in autumn. This is readily 
explained by the fact that in winter most of the ordinary supplies 
of water from the drainage of the surrounding country, are cut 
off by being converted into ice and snow, while evaporation from 
the surface of the lake by the dry northern winds continues to 
carry away a very sensible quantity of water. During the spring 
and early part of summer* the snow and ice melt, and the accu- 
mulated stores of winter, flow into the lake in greater quantity 
than to compensate for the evaporation and the drainage at the 
outlet. The summer of 1846 was remarkably dry and warm; 
that of 1847 more than usually cold and wet. <A small canal 
was cut some years since, from the head of the rapids at the Sault 
St. Marie, to supply the government saw mill near the foot of the 
rapids with water, and boats used to navigate this canal to the 
saw mill. In 1845 a little water entered this canal, perhaps eight 
inches to twelve inches in depth. In 1846 and 1847 the water 
did not ordinarily come within a foot or more of the level of its 
bottom. 
Ancient Levels of the Lake.—During a century past, the waters 
of Lake Superior cannot have been more than four feet above 
the level of the summer of 1847, for any considerable length of 
time. ‘This is evident from the growth of trees of two feet in 
diameter on Porter’s Island, within one hundred yards of the 
Government House that would have died had the ground around 
been inundated for any length of time. 
The evidences of higher levels of this lake in times more re- 
mote, but during the modern epoch, are numerous and striking. 
They consist in the beaches of shingle, and sand, and gravel, in 
successive elevations. The shingle and pebble beaches may be 
seen, well characterized, between Copper Harbor and Lake Fan- 
ny Hooe at Fort Wilkins, from the lake beach toa height of 
about forty feet. The sand beaches and dunes, may be seen at 
* On the 20th of June, 1847, snow still remained in the swamp on Porter's Isl- 
and, two feet in depth, over a sinal] area where the evergreen trees were 80 thick 
that the sun’s rays could scarcely pene 
