50 M. Savart on the Influence of different Media 



density are much less considerable than in the case of normal 

 vibrations. If we operate on rods or plates of glass, the 

 sounds produced in water, for example, differ the more from 

 those produced in air, that the plates are more narrow, while 

 their length and thickness are equal, so that we cannot deter- 

 mine, a priori, what will happen in each particular case. We 

 can make the sound descend a half tone, a tone, &c. 



From this it follows, that different media do not exercise 

 any appreciable influence upon the vibration of the faces of a 

 body which is the seat of tangential vibrations, and that, on 

 the contrary, they exert a very great influence on the vibra- 

 tions of those faces which produce normal vibrations, more or 

 less oblique. Those bodies, consequently, which, like vessels, 

 are formed of sides more or less oblique to the direction 

 of the vibrations, ought to present, when sounding in different 

 media, results very variable, and which it would be impossible 

 to predict in the present state of the science. Thus the sound 

 of a common drinking-glass is nearly an octave more grave 

 when sounding in water than in air, whilst in large glasses on 

 a foot, in the form of a cup, it may happen that the sound in 

 water is only one-twelfth more grave than in air. We may 

 conceive, indeed, that the descent of the sound will be as much 

 greater as the vessel presents more thin portions, having the 

 normal motions, as its sides are thinner, and as its diameter is 

 increased. But we may conceive, at the same time, the great 

 difficulty which there would be to determine rigorously the 

 laws of this kind of phenomenon, so as to predict what would 

 happen to any body whatever, when we wished it to sound in 

 any particular fluid. And what adds much to this difficulty 

 is, that the different media which surround a body influence 

 its number of vibrations, not only because they are more or 

 less dense, but because they vibrate along with it as a system, 

 a circumstance which alone ought to have a great influence. 



The modes of division of bodies which sound in different 

 media are invariable when they are affected only by tangential 

 longitudinal vibrations, but it is otherwise for normal vibra- 

 tions. If, for example, we fix a small rod of glass at the cen- 

 tre of a disc of the same substance, and perpendicular to it, 

 and if we produce a slight longitudinal friction on the small 



