Conducting Rods. 367 



mainmast was carried away in battle, by the fall of the foremast 

 across the main stay, which certainly might not have led to this 

 disaster, had the main-mast been in an efficient state. The loss 

 of all the mas(s was the loss probably of the ship." 



The British government at length resolved to furnish the nation- 

 al vessels with the most approved system of conductors, that of 

 Sir Win. Snow Harris. This measure was fully justified by the 

 result. For between the years 1828 and 1840, upwards of sixty 

 ships of the line had been exposed to lightning in all climates 

 without sustaining any damage ; while for the rest of the navy on 

 different stations and not so protected, there were damaged by 

 lightning, 7 ships of the line, V frigates, 30 sloops, and six smaller 

 vessels and steamers, in all 50 vessels, averaging more than one- 

 fourth of the British navy in commission. In a period of twenty- 

 two years, of the ships of the navy at sea, those without conductors, 

 compared with those with conductors, the number struck was in 

 the proportion of three of the former to two of the latter. 



Induced by such facts and considerations, the British govern- 

 ment in the year 1846, selected ten vessels to wear suits of light- 

 ning conductois, and sent them to different parts of the world and 

 into all climates during one year, and, finding every ship effectually 

 protected, before the year 1848, furnished every vessel in the 

 British navy with a similar protection, and the East India Com- 

 pany followed the example of the British government. 



The Committee therefore do not hesitate to declare their belief 

 that " the exemption of buildings from injury by lightning, through 

 the protection of lightning rods, has been such cts to justify the 

 general confidence reposed in them. 



2 Have not single trees and groves afforded greater protection 

 than the metallic rod ? 



It admits of no doubt that trees serve as natural conductors, and 

 especially those, of which the leaves are linear. A case in point 

 is quoted in Franklin's Letters. A Mr. "Wilcke saw a large fringed 

 cloud strongly electrified, and extending its inferior surface towards 

 the earth, which suddenly lost its electrical character in passing a 

 forest of tall fir trees. The ragged and dependent portions shrank 

 back upon the main cloud, and rose up as it were from the 

 earth. 



The conducting power of trees results only from the water they 

 contain ; for dry wood, especially when baked, becomes a non- 

 conductor ; water by the estimate of Mr. Cavendish, has to iron a 

 conducting power of only one to 400.000,000. 



