1 1 8 Mr. S. Sharpe on the tidelike Wave of Lake Ontario. 



The observations he records are : 



1st, Observed by Mr. Gourlay; at the Whirpool there was 

 a tide of three feet every four or five minutes. 



2ndly, by Dr. Bigsby; a mile below the Whirlpool there 

 was a flux and reflux of a foot every three or four minutes. 



3rdly, by Mr. Gourlay, confirmed by Dr. Bigsby; atQueen- 

 ston Wharf, on the river Niagara, there was a constant ebbing 

 and flowing of one foot in a minute. 



4-tlily, Related by Mr. Gourlay on the report of others, 

 that the tide of Nappanee took fifty minutes to flow and a 

 hundred minutes to ebb. 



Now if we suppose these undulations to be caused by the 

 wind, and that like water in a basin, when it is highest on one 

 side it is lowest on 'the other, the distance from shore to shore 

 will be similar to half the space between the tops of two waves 

 in the ocean, and having the distance given, we may by com- 

 parison with the pendulum learn the time of undulation. 



As the first and second observations were made at different 

 times, though at the same place, the wind had probably been 

 blowing with different force, which accounts for the disagree- 

 ment in the height to which the waves rose ; and might have 

 been blowing in different directions ; in one case more along 

 the lake, and in the other more across it, which might account 

 for the difference of the time. 



Let us compare these two observations with the theory, 

 neglecting the last two, which were made at different places ; 

 the third being on the river, which will account for the shorter 

 intervals between the flux and reflux ; and as there is no ob- 

 vious reason for the longer period of the fourth observation, 

 we may perhaps be allowed to think it less accurate, as being 

 related at third hand. 

 Making d = the distance from shore to shore, 



p = the length of a seconds pendulum 39*11 inches, 

 t = the time between high- and low-water, 

 we have by Newton's Princip. II. 4-6. 



d .<* 



8> 



and taking d, first = 171* miles the extreme length of the 

 lake, we have / = 6 T 2 ^j minutes. 



And again, d, as a minimum, at the average breadth of the 

 lake, = 35 miles, we have t = 2-j% minutes. 



These are the longest and shortest periods that can be al- 

 lowed for the undulation ; and as the first and second obser- 

 vations are within these extremes, they agree as nearly with 

 the theory as can be expected without further details. 



These 



