174 TEEES AS ELECTKIC AGENTS. 



hovers over the river valley, is seen to take the course of 

 the river in its journey toward the sea. Hence it is noto- 

 rious that in a very dry time the rivers obtain more show- 

 ers than the plains, and the wooded mountainous regions 

 more than the open and level country. And we may 

 regard it as a happy accident in the economy of nature, 

 that trees should be the most serviceable in nearly all 

 other respects, hardly less than as electric agents, upon 

 those situations which are of the least value for the pur- 

 poses of agriculture. Their branches on lofty ridges and 

 elevations, extending near the level of the lower clouds, 

 are like so many lightning-rods on the buildings of an 

 elevated city, and exert a powerful influence in conduct- 

 ing the electric fluid from an overcharged atmospheric 

 stratum, and preventing, in some degree those accumula- 

 tions that produce thunder-storms. Nature employs this 

 grand vegetable apparatus as one of the means of preserv- 

 ing that equilibrium, both of moisture and electricity, 

 which cannot be greatly disturbed without dangerous 

 commotions. 



I have said nothing of trees as a protection from light- 

 ning ; but there are many curious facts and superstitions 

 on record in relation to this point. "When a thun- 

 der-storm threatened," as Suetonius relates, " Tiberius 

 never failed to wear a crown of laurel-leaves, impressed 

 with the belief that lightning never touched the leaves of 

 this tree." The general opinion that certain trees are ex- 

 empt from the stroke of lightning is very ancient. It 

 probably originated in some religious ideas of their sanc- 

 tity, and men in more enlightened times have endeavored to 

 explain it by philosophy, instead of rejecting it as fable. 

 It was affirmed by Hugh Maxwell, an American writer, 

 that lightning often strikes the elm, the chestnut, the oak, 

 the pine, and less frequently the ash; but it always 

 evades the beech, the birch, and the maple. Captain 



