VIBRATION OF BODIES IN GENERAL. 363 



the notes produced by the transverse and longi- 

 tudinal vibrations of a rod. But this distinction 

 was employed by M. Felix Savart to express laws of 

 a more general kind ; and then, as often happens in 

 the progress of science, by pursuing these laws to a 

 higher point of generality, the distinction again 

 seemed to vanish. A very few words will explain 

 these steps. 



It was long ago known that vibrations may be 

 communicated by contact. The distinction of trans- 

 verse and longitudinal vibrations being established, 

 Savart found that if one rod touch another perpen- 

 dicularly, the longitudinal vibrations of the first 

 occasion transverse vibrations in the second, and 

 vice versa. This is the more remarkable, since the 

 two sets of vibrations are not equal in rapidity, and 

 therefore cannot sympathize in any obvious man- 

 ner 14 . Savart found himself able to generalize this 

 proposition, and to assert that in any combination 

 of rods, strings, and laminae, at right angles to each 

 other, the longitudinal and transverse vibrations 

 affect respectively the rods in the one and other 

 direction 15 , so that when the horizontal rods, for 

 example, vibrate in the one way, the vertical rods 

 vibrate in the other. 



This law was thus expressed in terms of that 

 classification of vibrations of which we have spoken. 

 Yet we easily see that we may express it in a more 

 general manner, without referring to that classifica- 



14 An. Chim. 1819, torn. xiv. p. 138. 15 Ib. p. 152. 



