304 Chi the Seiches of the Lake of Geneva. 



rents, such as M. Jurine formerly mentioned he had seen at the 

 Fosse- Vert, and such as every one may observe at all times un- 

 der the same circumstances. These flows will continue so long 

 as the pressure shall subsist with all its weight ; they will go so 

 far as to elevate the level of these still waters to the extent of 

 two feet and a half in the combination of circumstances that is 

 most favourable for their operation ; and then the pressure di- 

 minishing more or less rapidly, the swells moving along in some 

 other direction, it will speedily happen, that the waters may fall 

 as far as they before rose, if, at the same time, the amospheric 

 columns diminish in weight as much as previously they had in- 

 creased. 



This explanation accounts for all the appearances which the 

 seiches exhibit. Here we perceive why they are at their maximum 

 at the place where the current is the strongest, and are provided 

 with reservoirs to receive their superabundant waters; — that 

 they diminish in intensity in proportion as the declivity is less 

 considerable, and that at Genthod, where there is scarcely any 

 fall, the seiche also is scarcely sensible. It may, moreover, be re- 

 marked, that those of the ditches that are fed by the waters of , 

 the Rhone, below the bridges, such as Porte-Neuve, partake 

 of the phenomena of the seiche in the same way as the others. 



From this explanation we also learn, how the seiches are much 

 more considerable in the Lake of Geneva than they are in others 

 which have not the same configuration at their lower extremity ; 

 and why in these different lakes, they are more remarkable in 

 proportion as the waters have a swifter current at their exit, and 

 have in their neighbourhood a greater number of reservoirs 

 which can receive their superabundance. 



i When the atmospheric columns press unequally upon rivers, 

 and running waters of a considerable expanse, they do not pro- 

 duce seiches, at least any that can be perceived ; but they, at 

 the same time, retard or accelerate their course, according as the 

 waters are more or less pressed upon ; and they also produce, 

 without doubt, those refluxes, or counter currents, which can- 

 not often, as I believe, be explained on any other principle 

 And whenever the waters of a river, without any other probable 

 cause, are elevated or fall, we mav without hesitation conclude 



