IN Till-; N OUT II AMERICAN LAKES. 



15 



Detroit and at Buffalo. The mean annual average, however, is quite difibrent, 

 being- "reatcst at the cast end of the Lake. 



Me.vn Annual Difference for three years. 



Dkthoit. 

 Foet. 



1839 below 1838 1.33 



1840 " 1830 0.09 



1841 " 1840 1.00 



Full in three years 



3.32 



Buffalo. 

 Feet. 

 1.25 



1.25 

 1.05 



4.15 



Between the highest and lowest months within the 5'ear, the e.xtremes of fluctua- 

 tion are also quite different at different places. 



Greatest Difference of Level by monthly averages within a year. 



Clevki.and. 



Detroit. 

 Feet. 



2.33 



Buffalo. 



Feet. 



1.2'? 



2.30 



There is no way of eliminating such discrepancies, but by a more perfect series 

 of observations, and the rejection of such as are affected by sudden causes. This 

 cannot be done Avith the imperfect registers hitherto kept. 



I now pass to the third class of "fluctuations," namely, transient fluctuations. 



I shall here give some extracts from my memoranda upon the pulsations or oscil- 

 lations that occur on Lake Superior, in calm as well as in stormy weather. Those 

 of the 25th, 26th, and 27th of June, 1854, were very marked and regular. 



The Lake for several days was without storms, winds, or waves. The first table 

 is from observations made on the 29th of June. 



The same movement continued throughout the day. The place of observation 

 was within the creek called Eagle river, about twenty rods from the Lake. 



The flood or influx came into the stream, rapidly carrying boats, logs, and brush 

 violently against the current as far as the rapids. No storms or severe winds 

 occurred for several days before or after the 29th. The prevailing wind for the 

 month of July was from the west. For two weeks in the latter part of June and 

 forepart of July scarcely a day passed without the pulsations. 



The next table is from my register for October 11, 1854. The play of the 

 waters began early in the day, with a stiff south-easterly or off-shore breeze; and 

 no waves visible along the shore line. The observations were made in the o[ien 

 Lake, at the pier, in three feet of water, eight rods from shore. 



