and the effects of lightning on H,M.S. Rodney^ 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 tw’O 
lamince 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, 18S8'^. 
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 tnass of the hull and sea. The 
vane-spindle «r, 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 b, 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. 
