Resistance of Electrolytes at High Frequencies. 537 



layers o£ this element in the photosphere. The Fraunhofor 

 spectrum proves this " blanketing " effect. Sodium, in the 

 chromosphere, is subject to radiation which is deficient in 

 those particular wave-lengths which could put its atoms into 

 an abnormal state, whereas the effective wave-lengths for 

 barium are present. The effect o£ those types of radiation 

 present in the Sun's chromosphere is equivalent, therefore, 

 to a lower effective temperature or to a higher effective 

 ionization potential for sodium than for barium. 



Thus, Saha's treatment of the chromosphere as a black 

 body is but an approximation to the actual conditions, and 

 variations from the results of his treatment may be expected 

 because of the deficiencies in particularly effective types of 

 radiation as shown by the Fraunhofer spectrum. 



Palmer Physical Laboratory, 



Princeton University, U.S.A. 



LXII. On the Resistance of Electrolytes at High Frequencies. 

 By John J. Dowling, 31. A., F.Inst. P., and Katharine 

 . M. Preston*. 



§ 1. nPHE primary object of the experiments described in 

 J. this paper was to ascertain whether the resistance 

 of electrolytes is the same at high frequencies as for direct 

 currents. The problem was attacked as far back as 1889 

 by Professor (now Sir) J. J. Thomson f. He used a Hertz 

 oscillating circuit, and showed that at frequencies of the order 

 of 10 8 -^- there was good reason to believe that the ohmic 

 resistances of electrolytes were unchanged. As he pointed 

 out, there is an element of difficulty in reconciling these facts 

 with the ionic theory ot electrolytic conduction. The 

 problem, therefore, seemed worth further investigation, 

 particularly in view of the fact that we- had devised very 

 accurate methods for measuring resistances at hio-h f're- 

 quencies 



§ 2. These methods are developments of principles made 

 use of by the senior author in another connexion 1. 



The earlier experiments were carried out with a view to 

 testing the possibilities of the methods contemplated, and it 

 will, therefore, be convenient to describe the experiments 



* Communieated by Prof. J. Joly, F.E.S. 



+ Proc. Roy. tioc. vol. xlv., January 1889. 



X "A direct-reading- Ultramicrometer," Proc. Pov. Dublin Soc. xvi. 

 p. 185, March 1921 ; also Brit. Assoc, Edinburgh Meeting, 1921. 



