1840.] On Lightning Conductors to Powder Magazines. 270 



As the electric matter from violent storms causes intense heat., 

 it is recommended to have the conducting rods one inch in dia- 

 meter, which is a quarter of an inch more than they are usually 

 made in England. 



Strong wood brackets made of teak, or any other hard wood, 

 to keep the conductors firm in their places. 



There should be a conducting rod upon the principle here de- 

 lineated at each end of the building. 



And as the direction of lightning is often determined by that 

 of the rain, the surface on the side of the building might attract 

 it, it would be prudent therefore to have a conducting rod on 

 each side of the building as well as at the ends. 



The rods should be united with the best screwed joints, with 

 a top screw of the same metal as the conductor. 



XNo. 2.) 



From Assistant Surgeon W. B. CVShaughnessy, M.D. 

 To Capt. Debude, 

 Officiating Secretary Military Board. 



Fort William, December 27th, 1838. 



Sir, — I have the honor to acknowledge the receipt on the 24th 

 instant of your letter of the 22d, on the subject of the attach- 

 ment of lightning conductors to powder magazines. 



2. The question you propose is one of much difficulty. I 

 doubt indeed, whether the existing state of knowledge regarding 

 the reciprocal action of atmospherical and terrestrial electricity, 

 especially during the paroxysms of tropical storms, is as yet suffi- 

 ciently advanced to warrant the expression of more than a very 

 diffident opinion on its several points. 



3. I shall take the liberty of premising some general remarks 

 on lightning conductors, before I take up the special subject of 

 your letter. 



4. I am in possession of several facts hitherto unrecorded, 

 which seem to me clearly to show that in ordinary edifices 

 the attachment of lightning conductors, even" when properly 



