828 Dr. J. W. Nicholson on the 



The oscillation of the pressure did not exceed 0*12 mm. ; 

 the period of oscillation {i. e. from contact to contact) varied 

 from 6 sec. downwards. 



In conclusion I desire to express my thanks for the 

 facilities afforded me by the Physical and Chemical Depart- 

 ments of the University of Bristol, at which the research 

 was conducted. I am greatly indebted to Professor A. P. 

 Chattock and Dr. James W. McBain for constant advice, 

 and to the latter tor much personal assistance. 



References. 



1. Gouy, C. R., t. cxv. p. 720 (1892). 



2. Villard, C. R., t. cxxi. p. 115 (1895). 



3. Communications from Physical Laboratory at University of Ley den t 



No. 68, 1901 ; and Supplement 10, 1904. 



4. Cailletet & Collardeau, C R., t. cviii. p. 1280 (1889). 



5. Hagenbach, Ann. d. Physik, (4) B. v. S. 276 (1901). 



6. Eversheim, Ann. d. Physik, (4) B. xiii. S. 492 (1904). 



7. Travers <fc Usher, Proc. Roy. Soc, A, vol. lxxviii. p. 247 (1906). 



8. Wade & Finnemore, Journal of Chem. Soc, Nov. 1909, p. 1842. 



9. Ramsay & Youns:, Phil. Trans., A, vol. clxxviii. p. 57 (1887). 



10. Wolf, Mathias's"" Point Critique," p. 124 {Ann. de Ch. et Phys. (3) 



t. xlix. p. 270, 1857). 



11. Amagat, G R., t. cxiv. p. 1093 (1892). 



12. S. Young, Proc. Roy. Soc, A, vol. lxxviii. p. 262 (1906). 



13. Altschul, Zeit. Phys. Chem., B. x?. S. 578 (1893). 



14. Ramsay, Zeit. Phys. Chem., B. xiv. S. 486 (1894). 



15. Donnan, Brit. Assoc, Section B, 1904, p. 504. 



16. Kiister, Lehrbuch der physikalische Chemie, p. 1907. 



17. Dwelshauvers-Dery, Mathias's " Point Critique des corps purs," 



p. 230 (Pull, de VAcad. rot/, de Belyique, 3e se>ie, t. xxxi. p. 277, 

 1896). 



18. Andrews, Phil. Trans., A, vol clxxviii. p. 45 (1887). 



19. Mathias's '* Point Critique des corps purs," p. 213, Theorie ii. 



20. S. Young, Phil. Mag., vol. 1. p. 291 (1900). 



XC. The Accelerated Motion of a Dielectric Sphere. 

 By J. W. Nicholson, M.A., D.Sc* 



IN a previous paper, a brief account was given of the 

 motion of a conducting sphere whose mass is purely- 

 electrical, under the action of either a small uniform rield of 

 electric force or a small mechanical force. The solution was 

 deduced as a limiting case from a more general problem 

 treated by G. W. Walker f , and it was shown that there are 

 difficulties in the results of regarding any conductor as 



* Communicated by the Author. 



t Roy. Soc. Proc. A. vol. Ixxvii. p. 260 et seq. : Phil. Trans. A. 

 1910, p. 145 et seq. 



