20 Lamb, Waves in a Medium with Periodic Structure. 



The problem may be still further generalized by 

 imagining each interpolated system to have two distinct 

 points of attachment, on opposite sides, to the interrupted 

 string. The simplest example of this kind is" where each 

 system consists of two equal masses connected by a spring. 



-#WA/i^ 0>/wwu^ %m M\^ 



A dynamically equivalent problem is that of the propaga- 

 tion of sound-waves along a tube having a series of equi- 

 distant bulbous expansions. The difference-equation is 



found, on examination, to be of the same general type 

 (98) as before. 



