5156 



EXPERIMENTS AND INQUIRIKS 



Table Vlll. 



Diameter of the tube .1. A, B, C, and D, as in Table vii. 



Table IX. 



Diameter of the tube .3. 



A, B, C, and D, as in Table vii. 



Table x. 



A is the pressure. B, the distance of the 

 apex of the cone from the orifice of a tube . 1 

 in diameter. 



III. Ocular Evidence of the Nature of Sound. 



A tube about the tenth of an inch in dia- 

 meter, with a lateral orifice half an inch 

 from its end, filled rather deeper than the 

 axis of the tube, (Fig. 30,) was inserted at the 

 apex of a conical cavity, containing about 

 twenty cubic inches of air, and was 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 gal- 

 lons, with the same mouthpiece, 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 vibrations, which, when repeated with 

 sufficient frequency, impress on the auditory 



