1878.] Mr. J. E. H. Gordon on Electrical Constants. 155 



This correction, when introduced into my calculation of Mr. Dar- 

 win's problem, p. 182, will double the result, and give 19,350 years 

 to represent the 19,200 years, found by Mr. Darwin. 



I would wish to add, that Mr. Darwin, in a letter to myself, pro- 

 poses to call the cycloidal wabble described by him, a " lopsided 

 wabble,'" as distinguished from the simple circular "wabble" described 

 by me ; the one being caused by continuous motion of the axis of 

 figure, and the other caused by sudden displacement of that axis. 



V. " Measurements of Electrical Constants. No. II. On the 

 Specific Inductive Capacities of Certain Dielectrics." Part I. 

 By J. E. H. Gordon, B.A. Camb. Communicated by Pro- 

 fessor J. Clerk Maxwell, F.R. S. Received October 

 21, 1878. 



(Abstract.) 



A paper of mine with the above title was communicated to the Royal 

 Society by Professor J. Clerk Maxwell, F.R.S., on March 9th, 1878. 

 It was read on March 28th, and an abstract of it appeared in the 

 " Proceedings."* 



In the course of the summer it was pointed out to me that owing to 

 a mistake in the formula of calculation all the results were wrong. I, 

 therefore, requested permission to withdraw my paper, in order to re- 

 calculate the results. The new values of K arrived at led me to make 

 some determinations of refractive indices and to re-write the theoretical 

 deductions at the close of the paper. 



I now beg through Professor Maxwell to present the paper in an 

 amended form, in the hope that it may be found not entirely unworthy 

 of the attention of the Royal Society. 



As it would be impossible within the limits of an abstract to give 

 any intelligible account of the new method of experiment (due to Pro- 

 fessor Maxwell), which has been employed, I will merely give the table 

 of results, reserving all discussion and explanation until the publica- 

 tion of my paper in full. 



I may, however, state that the method is a zero method, that the 

 electrified metal plates never touch the dielectrics, and that the elec- 

 trification, which is produced by an induction coil, has an electromo- 

 tive force equal to that of about 2,050 chloride of silver cells, and is 

 reversed some 12,000 times per second. 



# Ante, vol. xxvii, p. 270. 



