378 



As time rolls on, the brightness of his individual virtues, the in- 

 cense of friendship, the adulation of contemporaries, will be slowly 

 disjoined from the literature of his works. They will be measured 

 by the more rigorous standards of rhetoric, and the canons of histori- 

 cal criticism; and his place will be more justly assigned him among 

 the writers of his age. Without that indiscriminating eulogy which 

 is unjust to others, simple justice will then rank him as the first of 

 the purely literary authors of his period. 



A communication was read from Col. Graham, dated Chi- 

 cago, July 19, 1860, relating to certain geographical deter- 

 minations, and the discovery of a lunar tidal wave in Lake 

 Michigan, as follows : — 



Chicago, Illinois, July 19, 1860. 

 To the Secretary of the American Philosophical Society, Philadel- 

 phia : 

 Dear Sir : I have made all the necessary astronomical observations 

 and electric sis-nals for determininc: the latitude and longitude of 



o C O 



twelve additional positions in the West ; but have been so pressed 

 with my public duties, that I have not been able to take up their 

 computation. When I can find time to do so, I will communicate 

 them, as heretofore, for the " Society's Proceedings.^' I find that, 

 in several instances, they will give results difi"ering much from those 

 given in the published maps. 



I have now nearly completed a paper, which I intend to offer for 

 publication in the " Society's Transactions," on the Discovery and 

 Demonstration of the Existence of a Semi-Diurnal Lunar Tidal Wave 

 on Lake Michigan. It is based on nine thousand one hundred and 

 eighty-four (9184) observations made on the tide-gauge, at Chicago, 

 of the elevation of the surface of this lake, between the 1st of Janu- 

 ary and the 1st of July, 1859. 



The observations were carried on uninterruptedly, both day and 

 night (except in a few instances, when violent storms would have 

 rendered them inaccurate), at intervals of half an hour, as a general 

 rule, and sometimes at intervals of fifteen minutes of time apart. 



From this series of observations we deduced the half-hourly (and 

 in two places the quarter-hourly) co-ordinates of altitude of the lake 

 surface, compared with the time (before and after) of the moon's 

 meridian transit, as follows. Here each co-ordinate, expressed in 

 decimals of a foot, is derived from a mean of three hundred and 

 forty (340) observations. 



