334 HISTORY OF ACOUSTICS. 



of the numbers of vibrations of different strings 

 may be determined from the numerical relations 

 of their notes. He had, therefore, only to deter- 

 mine the number of vibrations of one certain 

 string, or one known note, to know those of all 

 others. He took a musical string of three quarters 

 of a foot long, stretched with a weight of six 

 pounds and five-eighths, which he found gave him 

 by its vibrations a certain standard note in his 

 organ : he found that a string of the same material 

 and tension, fifteen feet, that is, twenty times as 

 long, made ten recurrences in a second ; and he in- 

 ferred that the number of vibrations of the shorter 

 string must also be twenty times as great; and 

 thus such a string must make in one second of 

 time two hundred vibrations. 



This determination of Mersenne does not ap- 

 pear to have attracted due notice; but some time 

 afterwards attempts were made to ascertain the 

 connexion between the sound and its elementary 

 pulsations in a more direct manner. Hooke, in 

 1681, produced sounds by the striking of the teeth 

 of brass wheels 4 , and Stancari, in 1706, by whirling 

 round a large wheel in air, showed, before the 

 academy of Bologna, how the number of vibra- 

 tions in a given note might be known. Sauveur, 

 who, though deaf for the first seven years of his 

 life, was one of the greatest promoters of the science 

 of sound, and gave it its name of acoustics, endea- 



4 Life, p. xxiii. 



