PAPERS ON CHEMISTRY AND PHYSICS 117 



tubes were different. These tubes were jacketed and 

 the pitch for various external lengths measured in the 

 manner described. The results of these observations 

 are also shown in Fig. 2. It is not possible to' draw 

 definite quantitative conclusions from the results ob- 

 tained. . The curves shown, however, indicate that the 

 pitch not only depends upon the absolute temperature, 

 but also that it varies according to a definite law involv- 

 ing the external length, and the other dimensions of the 

 tube. The observed data all fall on smooth curves, which 

 fact favors the possibility of such a law. 



