308 On Lightning Conductors to Powder Magazines. [No. 99. 



Can I be accused of exaggeration, when I express my belief, 

 that the same cause, which independently of direct discharge 

 occasioned the shocks here alluded to, might in a magazine of 

 powder barrels be sufficient to occasion minute sparks, and the 

 consequences to which these will naturally lead ? 



41. Lastly, M. Arago alludes to the proposition of Toaldo, 

 sanctioned by the Academy of Science, that for powder maga- 

 zines, the conductor should be placed at two or three metres 

 from the walls, on vertical masts. He approves of the idea in 

 principle, but describes its practical application as too expen- 

 sive, owing to the number of conductors which would be required. 



42. But there is one most important experiment by Prof. 

 Henry, of New York, to which I earnestly invite the attention 

 of the Board. I wish my humble voice could reach the Lords 

 of the Admiralty with effect, and that by an appeal to the 

 good sense of men, who have only public interests at heart, 

 and who have no previous scientific doctrines to combat for, that 

 I could induce them to pause before they provide the British 

 Navy with the dangerous conductors Mr. Harris has led them 

 to adopt. Professor Henry led a copper wire, forty feet long, 

 from the prime conductor of an electrifying machine, into a 

 deep well full of water. On working the machine, from every 

 part of this wire large sparks were obtained, and a voltaic 

 cannon was fired by one of these sparks close to the surface 

 of the water. Nay, more, Professor Henry repeated this ex- 

 periment on a lightning conductor attached to his house, and 

 properly constructed in every way. From every part of the 

 conductor sparks were given off. 



43. But even in the paper by Mr. Faraday, I find ample 

 admission of many of the facts I have contended for. " It is no 

 doubt true, that low rounded buildings, such as I understand 

 powder magazines to be in India, are but little liable to be 

 struck by lightning." " It is also I think very probable that 

 a lightning conductor may, under certain circumstances, cause 

 an electric discharge to take place, where none would have 

 occurred, no conductor being present." 



44. Let us hear what Mr. Daniell himself is candid enough 

 to allow. (See para. 1 1 of his report). 





