358 Mr. R Mallet on the Rate of 



cells with sulphate-of-copper solutions, the quantity — — — for 



the one-per-cent. solution at 20° C, we find this quantity 

 equal to 0*00082, while M. Wiillner* has found the same 

 quantity, 



For cane-sugar = 0*00070, 



For nitrate of potass... = 0'00229, 

 For sulphate of soda... =0'00236. 



From the chemical properties of sulphate of copper it is pro- 

 bable that, in this respect, it takes its place between cane-sugar 

 and the alkali-salts f. Experiments are in preparation in the 

 laboratory here for the purpose of obtaining more accurate 

 determinations. Meanwhile this calculation shows already at 

 least so much, that the consideration instituted gives a theoretic 

 value of the electromotive force which is of the same order of 

 magnitude as the observed. 



Since, moreover, factors obtained from the most various kinds 

 of physical investigations, and one of which amounts to above 

 a hundred millions, must be eliminated from both sides of the 

 equation, this preliminary result is still of some importance. 



XLIX. Rate of JEarthguaJce-ivave Transit. 

 By E. Mallet, F.R.S.% 



I PRESUME that I have been indebted to the politeness 

 of General Abbot, U.S. Engineers, for a copy of a paper 

 by that officer, published in the 'American Journal of Science ' 

 for March 1878. In this paper the writer recurs to his ac- 

 count of the experiments made at Hallet's Point on the occa- 

 sion of the great explosion there, on the rate of seismic-wave 

 transmission as described in General Abbot's paper read before 

 the American National Academy of Sciences, October 18, 

 1876, and also published as one of the papers of the Essayons 

 Club of the Corps of U.S. Engineers. Upon the results there 

 recorded I deemed it necessary to publish some remarks in the 

 Philosophical Magazine for October 1877, in which I pointed 

 out their anomalous character and their entire discordance 

 with each other. If I rightly gather General Abbot's meaning 

 from his last paper above alluded to, he considers that the 



* PoggendorfF's Annalen, vol. ciii. p. 556. 



t Supplementary Note (Jan. 1878). — Dr. J. Moser has since effected 

 determinations of the quantity in question, employing water and dilute 

 solutions instead of mercury. He obtained 0*00086 as the mean value 

 from ihree experiments. 



X Communicated by the Author. 



