Lightning-Conductors in Ships. 313 



othei-s become charged, until it becomes equalized through the 

 whole *. Now this process, which amounts in other terms to a 

 general diffusion of the electric matter through and about the 

 whole mass of the metal, cannot go on in any case so readily as 

 in that of an extended surface ; and it is doubtless on some 

 such principle as this, that we find mass is not requisite to elec- 

 trical accumulation. We can accumulate as much electric mat- 

 ter on a hollow sphere as on a solid sphere, so that at all times 

 it can more readily diffuse itself over a surface than penetrate 

 the mass. 



36. The circumstance of the conductor passing through the 

 ship is not an objection of any moment, taking, as in the former 

 cases, experience for our guide. It has been well observed in 

 the Transactions of the Royal Society, that, in cases of light- 

 ning on shipboard, no mischief has occurred after the explosion 

 has reached the well. That the action may be safely transmit- 

 ted through the keel to the water is evident ; it is, in fact, by 

 the metallic fastenings, which allow the electric matter a free 

 passage, that most of the ships struck by lightning are protected 

 from damage in the hull. We find this peculiarly the case in 

 his Majesty's fleet, where the metallic fastenings are in abun- 

 dance, and which being as it were connected with each other by 

 means of the mass of copper expanded over the bottom, the 

 whole action becomes rapidly equalized : it is not a little re- 

 markable, that the most common cases of damage in the hull 

 have occurred in merchant vessels, where such metalUc protec- 

 tion is not common. In further illustration of this protection, 

 we may cite the cases of his Majesty's ships London and Thetis, 

 both of which had their fore-masts shivered from the head to 

 the heel : now, as the electric matter did not stay in the ship, 

 how is it to be accounted for that the keelson and keel were not 

 split open as well as the mast, except for the reasons already as- 

 signed ? At the step of the mast we have immediately all the 

 keelson bolts to operate as conductors, and which connect with 

 the copper expanded over the bottom. Even in merchant ships, 

 protection is derived near the keel in a similar way by such me- 



• This is also well shewn by small lines of gold leaf stamiied on strips of 

 paper, so as to place the strips one over the other. 



.lULY — SEl'TIiMIiKR 1831. X 



