18 



FLUCTUATIONS OF LEVEL 



OscTLLATioNS. Aiigust 2rl and 3d, LS55. 



Such agitations of the water, in perfectly calm weather, attracted the attention 

 of travellers at an early clay. The relations of the Jesuit fathers are replete witli 

 accounts of sudden waves and swells, on which their canoes were tossed by sonic 

 invisible agent. All those who reside on the shores of the Lakes have made the 

 same observations. They have been so frequently noticed, and so often commented 

 upon in the public prints, that the subject has ceased to excite surprise. Even the 

 small Lakes of the interior sometimes exhibit the same mysterious movements, and 

 at times when neither storms nor winds are within view. But notwithstanding the 

 notoriety which they have acquired, there has been little direct observation. I 

 know of only two instances in past time in which registers have been kept. 



AVhen General Cass was at Green Bay in 1820, he caused the flux and reflux of 

 Avatcr at the mouth of the Fox river to be measured by a gauge set xipon the shor(\ 

 He concluded tlnit the fluctuations of level at that place had no connection with 

 lunar tides, and the observations show that tliey are not of tlie cla-ss wliich I have 

 recorded. 



The Eagle river tables show a uniformity and rapidity of motion quite different 

 from the Greeti Bay registers. Without going into details upon the nature and 

 cause of the changes of level at Green Bay, I will remark that a residence of one 

 summer at Fort Howard confirmed me in the correctness of the conclusion of 

 General Cass, in regard to the absence of any apparent effect from lunar attraction. 

 This appears to be the case in an estuary, whose shores terminate at an acute 

 angle, where very slight movements in the bay were made conspicuous at the point 

 of intersection of the shore lines. The general form of Green Bay is such tliat 

 the winds and currents of the open Ijake affect its surface from whatever direction 

 they come. The discharge of water from the Fox river is considerable, and tire 

 meeting of a wave of influx from the bay with this current would create an 

 observable rise. Vibrations would follow, which should occur as they are observed 

 to do, at irregular intervals of from half an hour to several hours. 



The only records relating purely to " barometrical waves," that I knoAV of, are 

 those of Professor Matlier, made at Copper Harbor in July, 18-17. He compared, 

 during one dav, tlu^ flui tuntions of his biironu'ter, with lliose of (he level of the 



