l.J.'J Official Correspondence on the attaching of 



2. Because a discharge may occur too great for the capacity of a 

 single conductor, in which case the electricity will divide itself to all 

 adjacent objects. 



3. Because though the discharge may pass to the ground, the lateral 

 electric disturbance may occasion an explosion within the Magazine. 



Dr. Faraday coincides in opinion with Dr. O'Shaughnessy on the 

 first point, remarking, however, that though Powder Magazines are 

 certainly but little liable to be struck, yet if they are struck the conse- 

 quent destruction and injury would be very great ; and that though it is 

 very probable that under certain circumstances a conductor may induce 

 a discharge where no discharge would take place no conductor being 

 present, yet he has the strongest conviction in his own mind that con- 

 ductors well applied, are perfect defenders of buildings from harm by 

 lightning. This opinion cannot but carry with it the highest authority, 

 and the irresistible evidence of authenticated facts alone could induce 

 us to adopt another. 



To the second of Dr. O'Shaughnessy's objections Dr. Faraday scarcely 

 alludes, though we feel warranted to infer from the language he em- 

 ploys in one part of his report that he admits its existence, since he 

 states as one of his reasons for preferring conductors of copper, that 

 " when struck it not only conducts the shock much better (than iron,) 

 "but in the predetermination of the stroke it determines more of the 

 " electricity to itself than would otherwise fall upon it, and therefore 

 " in any case of a divided shock, tends to leave less to fall elsewhere 

 "in the neighbourhood." The possibility of the division of the stroke 

 is fully admitted, but no notice is taken of the opinion involved in 

 Dr. O'Shaughnessy's statement, " that a discharge may occur too great 

 for the capacity of the conductor, in which case the electricity will 

 divide itself to all adjacent objects." The possible existence of division 

 is specified, the case or origin of division left unnoticed. Is it establish- 

 ed by satisfactory evidence that no such thing as a division of a light- 

 ning stroke prior to its impinging on a conductor takes place ? Is it 

 not possible that when a rod and an adjacent object are struck by the 

 same discharge that the strokes are independent of each other ? For 

 instance, did Dr. Goodeve see the conductor on Mr. Trower's house part 

 with its superabundant electricity to strike upon his own, or did the 

 electricity which followed the course of his window bolts impinge di- 

 rectly upon them? It appears to us important to make this distinc- 

 tion, and as we have not yet seen any facts, bearing specifically upon 

 it, we may be permitted to direct attention to it. If Dr. Goodeve did 

 not see the electricity leave Mr. Trower's conductor, we scarcely think 



