HOW LIGHTNING STRIKES TREES. 261 



HOW LIGHTNING STRIKES TREES. 



BY C. "W. HOPE. 



I DO not remember seeing the article in February's Forcstri/ 

 reprinted in the Indian Forester, and I do not see Forestry itself, 

 so I do not know whether any attempt was made in that article to 

 account for the various phenomena mentioned, 



Arago in his Meteorology (I write from recollection after 25 to 30 

 years) accounts for a tree being struck by the fact that owing to its 

 being full of sap it is a good conductor, and he says that the splinter- 

 ing is caused by the explosive force of the steam into which the sap 

 is suddenly converted. 



I do not think that Col. Pearson's theory fits in with the facts 

 I hav(3 observed. In 1871, I was at Simla during the rains, livin^' 

 in a house close to the church, and a deodar of about 2 feet diameter 

 (perhaps the largest then on the Simla ridge) just behind the house 

 was struck. The upper half of the tree, including most of the 

 branches, was knocked clean off, and the lower half was cleft widely 

 down to the ground, the bark being peeled off in large sheets. There 

 was not much splintering in this case, if I recollect rightly. In the 

 same month, June I think, a small deodar was struck in Simla, and 

 converted into matches, the bark being blown into fragments in all 

 directions and to some distance. This could hardly have been caused 

 directly by the lightning, which, the wet tree being a good conductor,., 

 must have passed into the ground ; but Arago's theory would 

 account for what happened, always supposing it possible that the- 

 sap of the tree could be so instantaneously boiled. 



Last year there was a notable case, when a large deodar near the 

 Municipal Hall, Mussoorie, was smashed to pieces. In all these- 

 cases, which happened in wet weather, the trees were quite moist, 

 but yet did not escape. 



Colonel Pearson thinks that a tree wh&n absolutely dry is nearly 

 a non-conductor, and his impression is that it is then shivered to 

 atoms. I presume he means when the bark is absolutely dry. But 

 the fact of the tree being struck at all shows that it is a conductor, 

 and this is mainly owing to the sap it contains. Is there any 

 instance of a dead tree having been struck ? I have heard of light- 

 ning having been seen in Mussoorie to fiy otf in sparks from a strip 

 of galvanized iron, used as the lightning-conductor of an iron-roofed 

 house, to a tree close by, to burn the leaves. — Indian Forester for 

 June, 



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