M. SAINTE-CLAIRE DEVILLE. 543 



rhythm in the movement of the falling water, were observed. This 

 was found to occur only at certain times. If the river was either too 

 high or too low, the water poured over the dam with regular and uni- 

 form motion and sound ; when the vibration of the houses occurred, 

 the pulsatory movement of the falling water was also noticed. 



The vibrations of the water were estimated at eight or ten per 

 second, or about half of the number required to give the lowest con- 

 tinuous sound. These facts being established, it still remained to 

 account for the enormous mechanical effect necessary to produce the 

 vibration of distant buildings. 



The long stretch of steadily flowing water above the dam, whose 

 sloping edge only partly arrested its course, suggested the divided cur- 

 rent of air thrown into the pipe of an organ. And, as the small column 

 of air in the pipe, when thrown into vibration, is known to produce in 

 some cases a perceptible tremor in the massive walls of a church, it is 

 probable that a column of water half a mile in length, when in rhyth- 

 mic vibration, would have a mechanical effect in proportion to its 

 mass. But, in order that such vibration of a considerable body of 

 water should be produced, a peculiar combination of physical condi- 

 tions must exist, and this I have never observed in any other place. 



Of course, the fall of such masses of water as pour over Niagara 

 and other great cataracts will cause a tremor of the earth to a certain 

 distance. But this is due to the simple mechanical force of impact, 

 and is in relation to that force only. The phenomenon which I have 

 described is intermittent, and that fact points to the conclusion that it 

 is due to a definite relation between the vibrations of the river and 

 what may be called the key-note of the bed-rock over which it flows. 



The distance to which such motion may be transmitted will, of 

 course, depend upon the mass of water in vibration. The direction 

 will depend upon the continuity of the underlying rock. Where this 

 is broken by seams, the vibrations will cease, and therefore the line of 

 these remarkable tremors affords an indication of the structure of the 

 granite bed which is the basis of the picturesque hills around Ellicott 

 City. 



M. SAINTE-CLAIRE DEYILLE. 



HENRI-fiTIENNE SAINTE-CLAIRE DEVILLE, one of the 

 most distinguished of French chemists, was born at St. Thomas, 

 in the Antilles, of French parents, March 11, 1818, and died at Bou- 

 logne-sur-Seine on the first day of July last. He went to France 

 while still a boy, with his brother, Charles Deville, the meteorologist, 

 and had his attention drawn early in his career in school to chemical 

 studies, which were then enjoying high credit under the brilliant results 



