Dr. L. T. More on Dielectric Strain. 527 



also suggest a possible explanation of the fact that the plane 

 of polarization is not always rotated in the same direction. 

 If the growth in the liquids is not uniform it is possible that 

 internal strains are set up so that one is really relieving 

 rather than producing a strain by compressing the tube. As 

 the rate of diffusion of gelatine is very slow, it is also possible 

 that the stirring which would produce uniformity in a crys- 

 talloid solution fails to do so here. 



Physical Laboratory, 

 University of Nebraska, Lincoln. 



LI. Notes on Dielectric Strain. By Louis T. More, Ph.D., 

 Professor of Physics, University of Cincinnati*. 



IN a recent number of the Philosophical Magazine, Dr. 

 Paul Sacerdote f has published a critique of a former 

 paper by mej, " On the Supposed Elongation of a Dielectric 

 in an Electrostatic Field," in which I stated that I had been 

 unable to notice any change in length in glass and hard 

 rubber-tubes when they were subjected to an intense electro- 

 static strain after extraneous effects had been eliminated. 

 Believing my experiments to have been carefully performed 

 I concluded that, if the effect exists at all, it must be exces- 

 sively small, and that the results of former investigators were 

 perhaps due, for the most part, to extraneous causes. Dr. 

 Sacerdote argues that this conclusion is unjustifiable, for, 

 " By the very disposition of his experiments the tube should 

 not experience any appreciable elongation ; thus the negative 

 result of his experiments merely proves that they were care- 

 fully performed." 



At the time I wrote my paper, I unfortunately was not 

 able to consult the recent and important work of Dr. 

 Sacerdote § and of Professors ( Jantone || and Sozzani^f. It 

 is on the experiments of these writers that Dr. Sacerdote 

 bases his theory and his criticism given above. He agrees 

 with me in this, that the results of Righi. Quincke, and all 

 former investigators are inaccurate and much too large. He 

 is, however, satisfied that Prof. Can tone's results are con- 

 clusive in proving the existence of the effect and the estab- 

 lishment of its law. 



* Communicated by the Author. 

 t Phil. Mag. [6] vol. i. pp. 357-359 (1901). 

 \ Ibid. pp. 198-210, August 1900. 



§ Annates de Phys. et Chem. ser. 7, t. xx. p. 289 ; Journ. de Phys. 

 ser. 3, t. viii. Sept.-Oct. (1899). 



|| Enid, d. R. Ace. dei Line. ser. 4, vol. iv. pp. 344, 471. 

 f Mend. d. JR. 1st. Lomb. ser. 2, vol. xxxiii. (1900). 



