and on the Defence of Shipping from Lightning. 175 



two laminae of copper sheet of considerable thickness and ex- 

 tension ; uniting them with the metallic masses in the hull by 

 other laminae, and giving the whole a perfectly free communi- 

 cation with the sea in all directions. The reasonableness of this 

 as an abstract question in electricity is quite evident; since all 

 the damage found to occur on ship-board from lightning 

 arises principally from the effects of expansion, where the 

 electrical discharge passes over or through bad conducting 

 matter. If we could conceive for an instant that the vessel, 

 sails, rigging, 8cc. were metallic throughout, the possibility of 

 its receiving any damage from lightning would be inconceiv- 

 able. 



This, in fact, has been shown by the perfect way in which 

 the iron steam-vessels in Lander's last voyage met discharges 

 of lightning whilst the timber vessels were damaged. The 

 nearer, therefore, we can approximate to this condition, the 

 more perfect the security. 



I satisfied the Navy Board, together with many eminent 

 scientific men of that day, of the completeness of my views, 

 and of their practical application to the variable conditions of 

 a ship's mast; and the celebrated Dr. Wollaston, in a letter to 

 the Comptroller of the Navy, gave my plan his "decided ap- 

 proval." Under these circumstances it was at last ordered 

 to be carried out in ten of H.M. ships, including line-of- 

 battle ships, frigates and corvettes; a small brig of 10 guns 

 was subsequently added to the list; and thus the conductors 

 were tried in the navy from the largest to nearly the smallest 

 vessel in it. After a period of ten years, during which time 

 these vessels had been exposed to several storms of lightning 

 in all parts of the world, the Lords Commissioners of the 

 Admiralty appointed, under the countenance of the House of 

 Commons, a commission of nautical and scientific men to 

 investigate and report on this momentous topic. The mem- 

 bers of the commission were all named without any reference 

 to myseltj and were all men of unquestionable integrity and 

 ability. When the names of Admiral Griffith, Sir James 

 Gordon, K.C.B., Captain J. C. Ross, Professor Daniell, Mr. 

 Fincham, and Mr. Clifton of the Admiralty, are mentioned, 

 no one of the least character in society would question the 

 fairness of any investigation placed under their direction. 



The Commission, in carrying out this measure, called in 

 evidence the officers who had commanded the ships in which 

 my conductors were tried, and obtained valuable information 

 from various others who had witnessed the effects of light- 

 ning at sea. They also invited the opinions of men acknow- 



