PLUCTUATIONS OF LEVEL 



NORTH AMERICAN LAKES, 



In the year 1838 a remarkable rise was observed in all the Lakes, since 

 which date I have neglected no opportunity to collect information concerning the 

 fluctuations of level that occur in these waters. For Lake Erie, by the assistance 

 of various observers to whom I have given credit in the proper place, I am now 

 able to present daily measurements for four entire though not consecutive years, 

 besides registers for parts of several years, and also to give some statistical tables 

 for other Lakes. 



The observations show three kinds of fluctuation. 



1. A general rise and fall, extending through a period of many years, which may 

 be called the secular variation of level, having no regular period of return, and 

 depending upon peculiar combinations in the meteorology of the country drained 

 by the tributaries to the waters of the great Northern Lakes. 



2. An annual rise and fall within certain limits, the period of which is completed 

 in about twelve months. This, which is caused by changes of the seasons within 

 the year, and can be predicted with much certainty, may properly be called the 

 annual variation. It occurs regularly, without reference to a general height of the 

 waters. 



3. A sudden, frequent, but irregular movement, varying from a few inclies to 

 several feet. This is of two kinds : one due to obvious causes, such as winds and 

 storms; another resulting from rapid undulations in calm water, the cause of which 

 is not yet satisfoctorily explained. Both classes may be styled transient fluctuations. 



In this paper I shall do little more than classify the statistics which I possess. 

 Meteorological registers for the Lake regions, owing to the recent settlement of 

 the country, are very scarce; and such as are to be found do not extend through 

 many years. The Army Meteorological Reports embrace the greatest length of 

 time, but reach no farther back than the year 1822. 



In the reports of the regents of the University of New York there is much 



valuable information on meteorology in general ; a part of which refers to the basin 



of the great Lakes. Half a centvu-y hence, when, by means of the records now 



established, a good annual abstract of the temperature, rain, and cloudiness of the 



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