412 REPORT— 1886. 



of gelatine in 150 cc. of dilute acetic acid, of strengtli one centigramme molecule 

 in 5 cc. 



Another paii- of similar tubes were fiUed with jelly made with 40 gi-ammes of 

 gelatine dissolved in 150 cc. of four times weaker acetic acid, viz., a centigramme 

 molecule in 20 cc. 



58 volts were applied to the carbon electrodes of all four tubes. The anode and 

 cathode vessels contained BaClj and CuSO^ respectively. 



In the tubes with weak acid, BaSO^ began to form in 88| hours after starting the 

 current, and its position was 19-3 in one tube, and 19-2 in the other, from the BaCl, 

 end, and therefore 19-7 and 19-8 from the Na„SO^ end. 



In the tubes with stronger acid the precipitate took some hours longer to form, 

 and its position was 19-2 in one tube, and 18-3 in the other, from the barium end. 

 The relative speed of travel of Ba in the two pairs of tubes was taken by making 

 simultaneous marks on each tube as the Ba proceeded ; and the ratio of these rates 

 was in the weak acid tube 1-21 times that in the stronger acid tube. 



_ Thus, although the absolute speed is less in the stronger acetic acid jelly (as is 

 quite right, because its conductivity is less ; see above), the ratio of the speeds of Ba 

 and SO4 remains practically unity in both. 



August 27. — To confii-m, the four tubes were started again in just the same 

 way, except that, while one pair contained jelly with O^HgO, centigramme mole- 

 cules in 5 cc. as before, the other pair contained jelly with C0H3O., centigramme 

 molecules in 40 cc. The distance travelled by Ba in the weak acid jelly tubes was 

 15 3 cm., and in the strong acid jelly tubes was 12-4 in the same time : firivine: a 

 ratio 1-20 as before. ' e b 



So far as it is wise to draw a moral from unfinished experiments it 

 may be said, that while there are some divergencies, yet they are in the 

 main confirmatory of the theory of Professor F. Kohlransch, especially in 

 the case of the velocity of hydrogen ; and I think it may be regarded 

 as a noteworthy instance of scientific prediction if numbers calculated 

 theoretically from conductivity data be found to agree at all closely with 

 the results of direct experiment. 



In conclusion, I wish to record ray best thanks to my assistant, Mr. 

 Edward Robinson, for the care and assiduity he has bestowed upon these 

 experiments. As I have had occasion to remark in the course of the 

 paper, he has not only carried out my proposals with ingenuity and skill, 

 but he has in several cases modified details and devised fresh combinations. 



CONTENTS. 



1. Mr. Thomas Gray, On Silver and Copper Voltameters. Communicated 



by Sir William Thomson (reference only) 308 



2. Professor Armstrong, On Electrolytic Conduction and Kesidual Affinity 



(reference only) 308 



3. Professor McLeod, On Ozone formed in Electrolysis (reference only) '. . 308 



4. Professor J. J. Thomson, On Ohm's Law in bad Conductors (note) . . 308 



5. Dr. John Hopkinson, On Continuity of Electric Conduction (letter and 



abstract) ............. 309 



6. Mr. Shelford Bidwell. On Diathermancy and Electrolytic Conductivity . 309 



7. Dr. Arrhenius, Letters on Electrolysis. Communicated by the Editor . 310 



8. Professor FitzGerald and Mr. Trouton, On Ohm's Law in Electrolytes . 312 



9. Professor S. P. Thompson, On the Electric Resistance of Magnetite . . 814 



10. Dr. Arrhenius, On Conductivity of Acid Mixtures SI.--, 



11. Mr. W. N. Shaw, On Verification of Faraday's Law for Silver and Copper . 318 



12. Mr. T. C. Fitzpatrick, On the application of Alternate Currents to Con- 



ductivity Determination. Communicated by Mr. W. N. Shaw . . 328 



13. Professor F. Kohlrausch, On the Conductivity of Electrolytes (abstract 



by Mr. Love) 334 



14. Dr. Lodge, Appendix to the same 337 



15. M. E. BouTY, Criticism on Professor Kohlrausch's Memoir .... 339 



16. Professor F. KoHLRAtrscH, Letter on the above criticism, et ceteris . . 341 



17. Dr. Arrhenius, On Viscosity and Conduction : Conductivity of Jelly . 344 



