and the effects of lightning on H,M.S. Rodney, 8)'c. 125 



fitting continuous conductors of lightning of great capacity in 

 the masts of ships, linking them by efficient communications, 

 together with the principal detached metallic bodies in the 

 hull, into one general continuous system, and finally connect- 

 ing the whole with the sea. These conductors consist of two 

 laminae of copper-sheet, varying from one inch and a half to 

 five inches wide, and being together nearly one-fourth of an 

 inch thick; they are inlaid so as to be fair with the surface of 

 the mast, and form a series of shut-joints ; they are otherwise 

 so constructed as to present an uninterrupted line of action 

 from the highest point to the sea. The method has been par- 

 tially used in the British navy for several years, and has been 

 proved in every way efficient. In no case has any of the ves- 

 sels fitted with them received the slightest damage, although 

 frequently exposed to severe thunderstorms, and in some in- 

 stances actually struck by heavy discharges similar to that 

 which fell on the Rodney in December, 1838*. 



20. If we consider attentively the effects of this shock, we 

 shall find them in complete accordance with the principles just 

 stated. The attendant phaenomena were of the simplest kind, 

 and such as have always occurred in cases of ships struck by 

 lightning not having a continuous conductor : e.g. the elec- 

 trical discharge, in forcing its way between the sea and clouds, 

 over resisting intervals, and between discontinuous metallic 

 masses, was productive of a violent expansive effect in these 

 intervals; causing at the same time a considerable evolution 

 of heat. There was really nothing particularly remarkable 

 in this instance ; the course of the discharge was a very simple 

 affair, being, according to the law of electrical action just ex- 

 emplified (Exp. 2), in the line or lines of least resistance from 

 the highest point to the sea : thus the course of the discharge 

 was, as represented in the annexed diagram, along the masts 

 and rigging, upon the general mass of the hull and sea. The 

 vane-spindle a, upon which the accumulation was first con- 

 centrated, was of course severely dealt with. From this, being 

 probably assisted by the moisture on the surface of the wood, 

 it glanced over the royal pole to the head of the top-gallant 

 mast at 6, where it found intermediate metallic assistance in 

 the copper funnel for the top-gallant rigging: from this, the 

 resistance in the mass of the wood appears to have been less 

 than that on its surface, probably from the long interval of air 

 between the funnel and conducting bodies about the cap be- 

 low, the mast was therefore split open as far as the cap at c. 

 Here again it was enabled to strike over the surface of the 



* See a letter in the Nautical Magazine for December 1839, by Lieut, 

 Sullivan, R.N., who witnessed these effects. 



