368 Conducting Rods. 



"Whether a grove would adequately protect a dwelling, depends 

 entirely ou the quantity of metal used in the construction of the 

 latter. It appears that the trees which have been visited by 

 thunderbolts have not been able to protect themselves. In other 

 words the obstruction to the current of electricity has been such 

 as to furnish no passage to a large quantity of the fluid, as in the 

 case of lightning rods badly insulated, which have been forsaken 

 by the fluid for a better conductor. 



Among the trees struck and more or less injured by lightning 

 the past year, have been noticed sycamores, pines, oaks, apple trees, 

 elms, and locusts. If trees possess a higher power of conduction 

 than a moistened bundle of wooden rods of the same heigth, it is 

 attributable to the increased evaporation from their- leaves and 

 branches ; especially is this true, when the electrical condition of 

 atmosphere is highly intense. By experiments, its has been shown 

 that a living plant evaporates from one third to one fourth more, 

 when electrified, than in its natural state ; so that not only the tree, 

 but its column of vapour, serves as an electrode through which 

 the positive electricity of the air passes to the earth Animals, in 

 like manner, by their profuse evaporation, greater than that o* 

 vegetables from their higher temperature, furnish better conduc- 

 tors than trees ; in confirmation of this, is the common direction 

 given in our scientific works, to avoid the shelter of trees. The 

 electricity, leaving the worse conductor the tree, selects the better 

 the animal. It may even be lured from a lightning rod of small 

 capacity, by a mass of the same metal of greater magnitude. 



Some facts furnished by Mr. Warner, before quoted, are here 

 available. 



He writes, " there were apple trees of good size on the North 

 and the South of the barn that was struck, at about the distance 

 of three rods. I have a barn 65 rods west of my house, which has 

 been struck ; the same shock went through an apple tree to a post 

 in a fence some seven feet from the tree, which it split and tore in 

 pieces. I could see no mark on the tree, but it has since died* 

 This tree is 30 feet from the barn. Six rods northerly is wood 

 land ; lightning has struck in these woods. I do not know of any 

 minerals in the land in this vicinity, which would attract the 

 lightning, but the land is rolling and of a strong moist soil." 



In South Abington, an oak was shivered, and a pine was struck; 

 and another in Reading. In Plymouth, an apple tree was struck. 

 In Exeter, a pine tree was cut off, and fell to the earth in an erect 



