98 Mr. G. Udny Yule. [June 15, 



extent, by Herr J. Bitter von Geitler* with an exciter of the type 

 used by Blondlot.f 



In the actual apparatus the wires were at F x run out through a 

 window in a loop of about 50 m. circumference round the labora- 

 tory garden. They re-entered the room at F 2 and were then run ver- 

 tically through the vessel for containing the electrolyte. The circuit 

 was completed by another loop, F 3 F 4 , 50 m. long, round the garden, 

 re-entering the room at F 4 , connecting to the electrometer at E, and 

 bridged at D, 2*25 m. = J\ from the electrometer. According to the 

 researches of Bjerknes (loc. cit.) these dimensions should be sufficient, 

 with the present apparatus, to prevent any sensible reaction. 



The electrometer was the same one as that used by Bjerknes in his 

 researches in the same laboratory. It is a simple quadrant electro- 

 meter with only one pair of quadrants and an uncharged aluminium 

 needle of the usual shape suspended by a quartz fibre. One quadrant 

 is connected to each wire. The needle taking no account of sign, 

 elongations are simply proportional to the time integral of the 

 energy : first throws, not steady deflections, are read. 



Various glass jars were used for holding the electrolyte. The wires 

 were run vertically through holes drilled in the bottom of the jar, into 

 which they were cemented. 



Several trials were made of this apparatus with dilute solutions of 

 copper sulphate. Headings were taken in pairs alternately, with no 

 solution in the jar and with some given thickness ; usually about ten 

 readings at each point. The ratio of the transmitted intensities so 

 obtained was determined for several points and plotted as a curve. 

 Some 5 or 6 cm. of electrolyte was the maximum thickness that could 

 be used in these first experiments. The curves so obtained for these 

 badly-conducting solutions always differed sensibly from the log- 

 arithmic, and the more so the more the solution was diluted. If the 

 mean log. dec. over the whole thickness was taken, the corresponding 

 value of the specific conductivity appeared extremely high. 



It appeared likely that these irregularities might be due to inter- 

 ference effects analogous to Newton's rings (by transmission), or the 

 phenomena of " thin plates," particularly in view of the results ob- 

 tained just previously by Mr. E. H. Barton in the same laboratory. 

 1 consequently desired to investigate for such interference pheno- 

 mena over as great a thickness of electrolyte as the absorption would 

 permit of using. Distilled water offered itself naturally as the best 

 electrolyte for this purpose. 



For the containing vessel a glass cylinder 114 cm. high was used; 

 the internal diameter varied somewhat, but was about 12 cm. at the 

 narrowest. 



* Doctor-Dissertation, Bonn, Jan., 1893, p. 22. 

 t ' Compt. Rend.,' vol. 114, p. 283, Feb., 1892. 



