and on the Defence of Shipping from Lightning. 179 



ignited by the electrical spark. This he calls a fair and 

 candid explanation of my experiments before the Navy Board 

 at Plymouth. 



As he gives every one who in any way treated this question 

 with fairness, a most liberal credit for ignorance, he thinks I 

 ought to have explained to the Board that a 'wire cotdd be 

 made red-hot by electricity, and if then brought into contact 

 with gunpowder woidd ignite it ; together with some other 

 truisms of a similar form. Now, however ignorant Mr. Stur- 

 geon may suppose the officers of the Board to have been, 

 they certainly understood the question much better than he 

 appears to do ; they entered very completely into its merits, 

 and left no point unexplored; they required of me informa- 

 tion relative to the conducting power of different metals; their 

 respective resistance to fusion by electricity; the ratio in 

 which they became healed, either by the same or by different 

 quantities, the relative quantities required to heat wires of 

 different diameters to the same degree, &c. &c. ; for the 

 perfect elucidation of which new experiments and apparatus 

 were invented, and the results exhibited in a way not before 

 done. 



Among other points to which the Board directed my atten- 

 tion, was the electrical effect of the incorporation of the con- 

 ductor with the mast and hull, and the certainty of its con- 

 fining the course of the discharge to certain lines and to the 

 surface of the masts without being productive of any lateral 

 effect upon the masses of the metal, such as iron hoops, bolts, 

 &c. which either entered into the body of the mast, or were 

 otherwise connected with it; points which Mr. Sturgeon, in 

 the happy consciousness of his own superior sagacity, says 

 were either " not known or unaccountably neglected." 



My first illustrations were confined to 'small models about 

 six inches in length, which could be splintered by artificial 

 discharges, and defended by smalllines of metallic leaf placed 

 along them, in imitation of the continuous conductor. But 

 being desirous to exemplify how completely the conductor 

 would direct and confine the discharge upon itself, I placed 

 the experiment under new and very delicate circumstances ; 

 and as I consider this experiment an important one, as bearing 

 on the theory of lightning conductors, and directly applicable 

 to all the objections made to them on account of lateral dis- 

 charges, I may, I hope, be excused for giving a particular 

 account of it. 



A model of a mast, M, about ten feet in length, was made in 

 parts, and an interrupted line of metal, a, b, c, d, placed in the 

 heart of it. Percussion povvder,which it is well known inflames 



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