respecting Sound and Light, 



115 















Table 



IX. 



A 



1. 15 



3-3 



4- 



B 



C 



•'5 



•3 



•5 



1. 



.06 



•15 



1. 



.06 



D 



D 



D 



D 



D 



D 



D 



D 



•5 

 1. 



.1 



.2 



.1 



.2 



.1 



.2 













2. 



3- 



•4 

 .6 



•35 



•5 



•34 

 •5 



• J 3 

 .2 



.1 



.1 



•'5 



.125 

 .18 



.1 



T^/e x. 



Diameter 

 of the tube 



•3- 



A, B, C, 

 and D, as in 

 Table vn. 



A 



B 



•4 



6. 



.8 



3- 



1.2 



i-5 



1 8 



1. 



2. 



•5 



4- 



•°! 



A is the pres- 

 sure. B, the dis- 

 tance of the a- 

 pex of the cone 

 from the orifice 

 5 of a tube .1 in 

 diameter. 



III. Ocular Evidefice of the Nature of Sound. 



A tube about the tenth of an inch in diameter, with a lateral 

 orifice half an inch from its end, filed rather deeper than the 

 axis of the tube, Fig. 27, was inserted at the apex of a conical 

 cavity containing about twenty cubic inches of air, and luted 

 perfectly tight : by blowing through the tube, a sound nearly 

 in unison with the tenor C was produced. By gradually 

 increasing the capacity of the cavity as far as several gallons, 

 with the same mouth-piece, the sound, although faint, became 

 more and more grave, till it was no longer a musical note. 

 Even before this period a kind of trembling was distinguishable; 

 and this, as the cavity was still further increased, was changed 

 into a succession of distinct puffs, like the sound produced by 

 an explosion of air from the lips ; as slow, in some instances, as 

 4 or 3 in a second. These were undoubtedly the single vibra- 

 tions, which, when repeated with sufficient frequency, impress 

 on the auditory nerve the sensation of a continued sound. On 

 forcing a current of smoke through the tube, the vibratory 

 motion of the stream, as it passed out at the lateral orifice, was 

 evident to the eye ; although, from various circumstances, the 

 quantity and direction of its motion could not be subjected to 



O 2 



