On the Seiches of the Lake of Geneva. 287 



attraction. It might depend on some obscure law of physics or 

 of atmospheric electricity ; and the discovery of the cause could 

 not fail to be highly gratifying. I prepared myself then seri- 

 ously for the work ; and was really in that state of mind which 

 philosophers recommend'when in the search after truth. I had 

 not as yet formed any hypothesis upon the cause of the Seiches, 

 and my only knowledge about them consisted in the descriptions 

 of authors, and in the recollections of what I had seen of them 

 in my early youth. 



My first observations bear date of the beginning of November 

 1802. Prepossessed with the idea that ihe Seiches did not occur 

 but at some short periods of the year, and especially at the time 

 when the waters were most abundant, I went often to the shores 

 of the lake, less for the purpose of observing the phenomenon, 

 than of establishing its absence at this season of the year. But 

 as on every occasion, instead of being stationary, the waters had 

 a marked rise and fall, I saw it was essential to give my obser- 

 vations the necessary accuracy. I shall here remark, before go- 

 ing further, that the movement of elevation and of depression of 

 which we are now speaking can never be confounded with that 

 of the waves. It does not at all exhibit itself by any agita- 

 tion on the surface of the water ; on the contrary, it is a calm 

 and simultaneous movement of the entire liquid mass. It alike 

 takes place when the water is agitated, and when it is calm ; but 

 to observe it accurately in the first instance, without any fear of 

 confounding it with the motions of the waves, I directed a por- 

 tion of the water into a small pool, where its tranquillity could 

 not by possibility be so affected. 



I was not satisfied with observing in general the movements 

 of the water, whether rising or falling ; I was also solicitous of 

 marking the duration of their movements, and the laws they fol- 

 lowed. I therefore provided myself with a French foot-rule, 

 which I placed perpendicularly in the water, several inches 

 above its surface, so that I could perceive each minute, the 

 changes of the level. I thought it equally necessary to note, at 

 the commencement of every observation, the condition and me- 

 teorological circumstances of the atmosphere. With regard to 

 the height of the barometer, I followed the tables of the Biblio- 

 theque Briiannique, which supplies two diurnal observations. 



2u 



