XIX. 



On a mistake which exists in the calculation of Mr. Poisson rela- 

 tive to the distribution of the electrical matter upon the surfaces 



two globes : in vol*i2 of the " Memoires de la classe des 

 sciences mathematiques et physiques deVlnstitut Imperial de 



France.''^ 



By NATHANIEL BOWDITCH, LL. D. 



N the second memoir of Mr. Poisson, published in the ahove 

 volume (which the reader of this article ought to have lying he- 

 fore him) is given a series to fiad the thickness of the electric, 

 al stratum upon the surfaces of two globes brought nearly in 

 contact with each other. In the course of this calculation when 



finding the value of S' (page 245, line l6j the integral /-j^^— is 



multiplied by the factor 18 — -+^-^, instead of which the 



simple factor - ought to be used. This affects the calculation in 

 several of the expressions in the subsequent pages of that work. 



Thus (in page 246, line 5) the two first terms of H become 



5 3^/7 5a 



- — rrj \ being exactly the same, 



126 — 6" V-^^O ■" It) (a + 6) 8 (a + hf 



except in the signs, as the two first terms of H', (page 247, line 

 18,) so that when these terms are added together, to obtain the 

 value of ij, (page 248, line 3,) the coefficient of A ^ vanishes, 

 as well as those of h! and fe ^', leaving only the term H h' T^ (af- 



% 

 ^ 



