118 Mr. Snow Harris on Lightning Conductors 



metallic conductors have been from any cause placed along 

 the masts or rigging, and in which the electric agency found 

 its way through the hull to the sea. We should further ex- 

 pect from him, something like an examination of the general 

 nature and effects of electrical discharges, since it is clear, be- 

 fore any accurate estimate can be arrived at, of the relative 

 quantity of electricity likely to be discharged from a thunder- 

 cloud, and the probable effects on metallic rods, or other 

 conductors set up with a view of directing it in any given 

 course, such information is quite indispensable. 



4. Now it is to be particularly observed, that Mr. Sturgeon's 

 memoir is really deficient in such information ; a few clumsy 

 experiments in illustration of a well-known fact in electricity, 

 deceptively associated, by means of a vague hypothesis, with 

 some of the ordinary effects of lightning, on a ship not having 

 any regular conductor, and with some every-day phaenomena 

 of the electrical kite, is virtually the amount of all thattheauthor 

 has advanced, under the imposing title of " Theoretical and 

 Experimental Reseaixhes." ., 



5. In illustration of the careless way in which he meets this 

 question, it may not be out of place to notice the following- 

 specimen of his inductive philosophy, —being the very outset 

 of the comparison he has proposed, of the observed effects of 

 lightning, and the probable effects on my conductors*. 



In the account given of the damage recently sustained by 

 H.M. Ship Rodney, it appears, that the shock of lightning 

 which shivered the top-gallant-mast, damaged the top-mast, 

 &c., &c., fell on a small brass sheave in the truck for signal 

 halliards, and slightly fused it. This sheave weighed about 4? 

 ounces ; it was only about an inch and a half diameter, hol- 

 lowed except at the centre and rim, where it was somewhere 

 about half of an inch in thickness. The lightning also fell on 

 the copper funnel for top-gallant rigging, being a hollow 

 cylinder of 16 inches in length, 10 inches in diameter, and not 

 quite a quarter of an inch thick. This funnel was not any- 

 where fused. It fell also on other metallic masses, such as the 

 iron-bound tie-block, on the top-sail-yard, &c., &c., the iron 

 hoops of the mast, &c., on which no calorific effect was ap- 

 parent. 



6. Now we have here something like evidence what was 

 really the actual jpower of the charge. We see, for example, 

 that it did not fuse a copper funnel, 16 inches long, 10 inches 

 in diameter, and about J^th of an inch thick. In the face of 

 which fact Mr. Sturgeon insists, that had the charge fallen on 



"^ Sturgeon's Memoir, sec. 204. 



