Experiments on the Velocity of Sound in Air. 329 



In Dulong's experiments care was taken to obtain pipes of 

 good tone ; but my experiments have convinced me that such 

 a tone is the worst possible for measurement of wave-lengths. 

 A good musical tone is not pure in the acoustical sense, and 

 the presence of the partials constrains the pitch of the prime to 

 some extent. If the form of pipe were such that its proper 

 tones agreed exactly with the harmonic series, there would 

 not be this difficulty of constrained pitch ; but as it would 

 have been exceedingly difficult to construct pipes of this 

 character, I determined to introduce a bulb or pear-shaped 

 portion between the speaking-mouth and the cylindrical tube 

 in which the sliding-plug worked (see Plate VII. fig. 1). By 

 this means tubes were obtained having proper tones quite out 

 of the harmonic order, and therefore capable of giving very 

 pure prime tones. 



In November last it was stated that the results obtained from 

 the 11*43 millim. tube were not very reliable. The experi- 

 ments with this tube have been repeated, and a new tube of 

 88*19 millim. diameter has been introduced, completing a 

 series of five tubes, ranging in the proportion of 3 to 5, from 

 11*43 to 88*19 millim. diameter*. The results of the new 

 experiments are given in the following table : — 



Table IV. 

 Velocity of Sound in dry Air, at 0° C, in tubes. 



Diameter of] 

 tube J 



1143 millim. 



88-19 millim. 





324-533 

 324-234 



330-29 

 330-46 

 330-02 

 329-72 

 329-99 

 330-41 

 33009 

 33006 

 330-10 

 330-20 



Means 



324-383 



330-134 



In Table V. the results of all the experiments are brought 

 together : — 



* Through a clerical error the diameters of the tubes were previously 

 given as 11-7, 19-5, 32-5, and 54'1 millim., instead of 11-43, 19-05, 31*71. 

 and 52-91. 



Phil. Mag. S. 5. Vol. 18. No. 113. Oct. 1884. Z 



