1 72 Mr. Snow Harris on Lighbiing Conductors, 



If we return to the values (2.) (3.), 



k = ^-^ ^ = !^, (62.) 



we have obviously 

 J_ 



(¥)' 



and on substituting in the form (61.) we obtain 



<7r A jr> 

 I / sin"' I 



which for abridgement may be expressed by 



the formula for the dispersion. 



(11.) 1 have here confined my remarks strictly to the illus- 

 tration of the one primary question of the criterion of elliptic 

 polarization ; but in all that has been said relative to the evane- 

 scence of the terms on the hypothesis of symmetrical arrange- 

 ment, by the transference to new axes, &c., I have touched 

 upon the far more extensive relations between our immediate 

 subject and that of the axes of elasticity and the wave-surface : 

 some remarks on these must be reserved to a future commu- 

 nication ; meanwhile I will venture to hope that the particular 

 subject of the preceding observations has now been placed in 

 such a light as to free it from the ambiguity and doubt in 

 which it seems to have been involved. 



XXXIII. On Lightning Conductors, and on Experime7its relat- 

 ing to tlie Dtfence of Shipping from LightJiing. By W. 

 Snow Hahris, Esq., F.R.S. 



To the Editors of the Philosophical Magazine a?id Journal. 



Gentlemen, 



YOU will greatly oblige me, by allowing the following com- 

 munication to appear in the pages of your Journal, being 

 the concluding observations I have to offer on Mr. Sturgeon's 



