WILLIS'S VOWEL MACHINE. 271 



he could entirely dispense with 'the introduction of the 

 hand, and could obtain the whole series of vowels, by 

 sliding a flat board C D over the mouth of the cavity. 

 Mr. Willis then conceived the idea of adapting to the reed 

 cylindrical tubes, whose length could be varied by sliding 

 joints. When the tube was greatly less than the length 

 of a stopped pipe in unison with the reed, it sounded I, 

 and by increasing the length of the tube it gave E, A, 

 and U in succession. But what was very unexpected, 



Fig. 49. 



when the tube was so much lengthened as to be 1J times 

 the length of a stopped pipe in unison with the reed, the 

 vowels began to be again sounded in an inverted order, 

 viz., U, 0, A, E, and then again in a direct order, I, E, A 

 O, U, when the length of the tube was equal to twice that 

 of a stopped pipe, in unison with the reed. 



Some important discoveries have been recently made by 

 M. Savart respecting the mechanism of the human voice,* 

 and we have no doubt that, before another century is 

 completed, a Talking and a Singing machine will be 

 numbered among the conquests of Science. 



* See Edinburgh Journal of Science, No. viii. p. 200. 



