18 W. W. Mather on the Meteorology 
A heavy rain storm from the n. and n.w. succeeded on the fol- 
lowing day 
Many observing men on the lakes have noticed that the extra- 
ordinary variations in the level of the water precede a storm. I 
regret that I did not accurately note down more of them. ‘The 
preceding notes may call the attention of those favorably situated 
for these investigations, carefully to observe the attending circum- 
stances, and especially the barometric fluctuations, wind, weather, 
and temperature. A rise of the barometer in the annulus of a 
storm precedes the depression, and would account for the fluctua- 
tions of level, whether the variations in atmospheric pressure 
occur at the place of observation or at some distant point, on a 
broad expanse of water. 
Periodical Rise and Fall of Lake Superior.—The gradual rise 
and fall of the level of the water in the great lakes, through a 
series of years, has long been noticed. Its cause is doubtless due 
to a greater quantity of rain and snow, or of a lower mean of 
temperature and diminished evaporation during the pericd of rise, 
and the reverse during the time of fall of the water-level of the 
Jakes. During the year 1838 or 1839, the waters were higher 
than they had been before for at least two centuries. This is 
demonstrated by the large tracts of land that were inundated, 
which are covered with forest trees, many of them the growth of 
ages. ‘These trees were destroyed by this overflow around Lakes 
Erie and Huron and on the St. Mary’s river, between Point De- 
tour and the Sault St. Marie. 
We have no accounts of Lake Superior at that time, and I have 
seen no similar tracts of destroyed timber on the shores of that 
lake, although I have coasted along most of the shore. There 
are facts however that indicate a marked variation within a few 
ey In 1845 a rock in the middle of the entrance of Eagle 
Tarbor showed itself only in the trough of the waves; and the 
narrow inlet betwen the west end of Porter’s Island and the 
main land at Copper Harbor, was of such depth that loaded Mac- 
inaw boats could enter Copper Harbor without touching the rocks. 
In the summer of 1846 the rock at the mouth of Eagle Harbor 
was a foot and a half above water; boats could not get into Cop- 
per Harbor through the inlet above mentioned, and skifls and 
canoes rarely attempted to enter by that passage. In June, 1847, 
the rock above mentioned was still more out of water, and the 
western inlet to Copper Harbor could be crossed, by stepping on 
the projecting points of the reef, without wetting the feet ; and 
during some depressions of the water by barometric waves, it 
was laid almost entirely dry. From the 18th of June to the 6th 
of September the general level of the water rose fully twelve 
inches. Several large rocks in the water Opposite the govern- 
ment house, with their points projecting at different heights above 
Ny 
