Stress and Strain on the Properties of Matter. 



101 



The velocity of sound as calculated from the values of e' s and the 

 density would in no case differ from those obtained directly by so 

 much as J per cent. 



The Velocity of Sound is Independent of the Temporary Load. 



Experiment VIII. 



A well annealed copper wire about 1 mm. in diameter was weighted 

 with 18 kilos, and left with this load on for some time. It was then 

 tested with various loads up to 18 kilos, with the following results. 



Load on the wire before 

 clamping. 



Number of longitudinal 

 vibrations in three 

 minutes.* 



6 kilos. 



4048 -5 x 20 



10 „ 



4056-3 



14 „ 



4054 -9 



18 „ 



4057 



Mean of last three. . . .' 



4056 -1 



It is evident from the above that except for the lightest load, the 

 velocity of sound is entirely independent of the temporary load, and 

 even with the load of 6 kilos, there is not a departure from the mean 

 value obtained with the other three loads of more than 0"2 per cent.f 



Similarly with a pianoforte steel wire of 0*08 cm. diameter, not the 

 slightest difference in the pitch of the note could be discerned with 

 loads which varied from 16 kilos, up to 30 kilos. 



The temporary alteration of density which w r as produced in either 

 of these two experiments would be too small to cause of itself a 

 perceptible alteration of pitch. Thus in the case of the piano-steel 

 wire, the temporary change of density resulting from the increase of 

 the load from 16 kilos, to 30 kilos, would only cause a change in the 

 pitch of the note of 03 per cent. 



The Effect of Permanent Extension on the Velocity of Sound. 



The author has shownj that when an iron wire has recently suffered 

 permanent extension the longitudinal elasticity as determined by the 



* The numbers in this column are the means of several observations with each 

 load. 



f The note with the load of 6 kilos, was not quite so clear as that obtained with 

 the other three loads. 



X 'Phil. Trans.,' vol. 174 (Part I), 1833. 



