October 18, 1901.] 



SCIENCE. 



595 



These solutions are as fluid as water, 

 but still behave optically as quasi-solids, 

 capable of sustaining a static strain without 

 a displacement of the mobile particles. 

 This condition is reached very slowly and 

 the depolarization early in the formation 

 indicates that the progress of formation of 

 the solid structure is not homogeneous, but 

 that it later becomes so, as indicated by the 

 disappearance of the depolarization. 



26. ' Notes on Dielectric Strain ' : Louis 

 Trenchard More, University of Cincinnati. 



This paper — ' Notes on Dielectric Strain ' 

 — is an answer to a paper by Dr. Paul Sacer- 

 dote (Philosophical Magazine, March, 1901), 

 criticizing an article by me which appeared 

 in the Philosophical Magazine for August, 

 1900. In attempting to extend the work 

 of Quincke and others who found that 

 glass, when electrified, elongated propor- 

 tionally to the square of the difference of 

 potential and inversely as the square of 

 the thickness of the dielectric, I noticed 

 that after errors were eliminated the efiect 



vanished or was at least less than^ =10~'^ 



— a result much less than that found by 

 former investigators. My work attracted 

 the attention of Professor Cantone and Dr. 

 Sacerdote, the latter of whom had recently 

 published a theoretical discussion of the 

 subject. This theory is based on a coefii- 

 cient which expresses the relation between 

 the potential and the elongation and so 

 fails if the elongation is eliminated. Dr. 

 Sacerdote's criticism showed, I thought, 

 that he had not understood my results and 

 had underestimated the delicacy of my 

 apparatus which seems fully capable of re- 

 cording the changes of length noticed by 

 the most accurate of former investigators — 

 Professor Cantone. 



I have in these papers shown that my 

 apparatus was capable of measuring the 

 efiect — that it did record an efiect similar 

 to that noted by other investigators, but 



that this efiect was due to bending of the 

 glass tube by electrostatic attraction — that 

 this error being eliminated the efiect van- 

 ished. 



The sources of errors of former investi- 

 gators are probably the following : 



1. No adequate precautions were taken 

 against lateral bending of the tube. The 

 changes of length produced by an extremely 

 small deflection would account for the en- 

 tire amount of the efiect. 



2. The elongations are too close to limit 

 of observation to establish a law when the 

 efiect itself is still questionable. 



3. Changes of length on charge and dis- 

 charge are not equal. This difierence some- 

 times equals 40 percent, of the entire change. 

 An extraneous effect of such magnitude 

 casts doubt on the cause of the elongation. 



4. With each investigator, using im- 

 proved and more delicate apparatus, the 

 amount of the effect steadily decreases. 

 This points either to a partial or entire 

 influence of extraneous causes. (To be 

 printed in the Philosophical Magazine. ) 



27. ' The Temperature Gradient of the 

 Atmosphere, with Formula ' : S. R, Cook, 

 "Washburn College. 



The author calls attention to the diffi- 

 culty, in discussing the escape of gases fiom 

 the atmosphere, of determining the tem- 

 perature of the station in the upper atmos- 

 phere under consideration. 



From the kite observations of the United 

 States Weather Bureau and the recent bal- 

 loon ascensions at Paris, it was shown that 

 the rate of decrease of temperature with 

 altitude was not constant. 



From balloon ascensions made March 24, 

 1899, near Paris, an experimental formu'a 

 t^ = t^fi~-^'' was obtained for the temperature 

 gradient when t^ and t^ are the absolute 

 temperatures at positions whose distances 

 from the surface are x, and at the surface 

 respectively, and when ^ is a constant ob- 

 tained from the balloon ascensions. 



