304 ILLINOIS STATE ACADEMY OF SCIENCE 



The same figure also shows the corresponding vibration 

 frequencies (indicated by crosses) plotted to the same scale 

 against absolute temperatures. This relation also seems 

 to be linear except for the point taken at 91° absolute. The 

 pitch was determined by means of a tone variator. 



Lastly the vibration frequencies and temperature aif- 

 ferences in degrees centigrade, as shown by the graphs, are 

 nearly equal numerically. This, however, should be con- 

 sidered as a coincidence. 



Observations with tubes of different pitches and extend- 

 ing over wider temperature ranges are under way. 



Department of Physics 

 University of Illinois 

 February, 1921. 



