J 840.] On Liyhtning Conductors to Powder Magazines, 293 



risk of failure ; and it is a point of very little importance, pro- 

 vided absolute protection be assured.* 



Moreover a rod of a less diameter would scarcely have suffi- 

 cient strength to resist the mechanical forces which might be 

 opposed to it. 



18. The rod should be of copper, first, because the conducting 

 power of that metal is very much superior to that of iron, being 

 in the proportion of 1000 to 158. And, secondly, it is little liable 

 to oxidation and corrosion. I do not think that the application 

 of zinc to iron rods, in the way proposed by Dr. CTShaughnessy, 

 would be, by any means, efficient in keeping them bright, at the 

 same time I would rather erect iron conductors, than run the 

 risk of a total want of protection. 



19. I have no objection to make the disposition of the con- 

 ductors proposed by Dr. O'Shaughnessy, but I see no reason for 

 placing them at so great a distance as twenty paces from the 

 magazine. The most material points to be attended to, are their 

 perfect metallic continuity, and their communication with the 

 water of the subsoil. The instructions for the erection of light- 

 ning conductors are so minutely detailed in the two reports to 

 which I have already referred, that I think it unnecessary to add 

 any thing more at present, but it will give me the greatest 

 pleasure to afford any further explanations in my power that 

 may be required. 



I cannot conclude, without again expressing my strong con- 

 viction of the necessity of procuring a revision of the opinion of 

 the Governor in Council upon the subject in question with as 

 little delay as possible. 



I have the honor to be, &c. 



(Signed) J. F. Daniell. 

 To Philip Melvill, Esq. 

 &c. &c. &c. 



* I did not allude to a single conductor, but to a set of several combined. 

 -W. B. OS. 



, 



