Electric Currents 71 



premature dropping of leaves and dying of branches occur 

 above the affected root. A characteristic outward sign for 

 diagnosis is the darkening and rapid loosening and falling 

 of the bark, similar to what occurs in the case of kerosene 

 poisoning. 



If the leak is a sudden one and the gas escapes in a large 

 quantity, a tree in full foliage may suddenly have its leaves 

 droop and turn brown; these hanging on, however, till 

 winter winds tear them off; such trees die in short order. 

 In some cases trees have been known to have been kiUed 

 by gas in a single night. 



If, however, the leak is slow and small, only a single root 

 and its corresponding crown parts may be killed, but, if 

 the leak continues and the gas spreads in the soil — which in 

 loose soils may go on raj)idly for a thousand feet or more, 

 ■ — general debility develops and the whole tree gradually 

 succumbs. There is practically no recovery for a tree once 

 severely poisoned in this way, for the soil is saturated with 

 gas, the roots are killed, and it is practically impossible to 

 renew the soil. 



Watering, which has been proposed as a remedy, does 

 not seem to counteract the poison. If detected in time, 

 renewal of the soil, root pruning, and severe cutting back 

 may restore the patient. 



Electric Currents. The appearance of trees killed by 

 gas is very much the same as that of those killed by light- 

 ning or electric currents, the foliage dying and remaining 

 hanging on the tree. This takes place not necessarily only 

 on trees which show the lightning stroke along the trunk, 

 but also as a result of general electric conditions of the 

 atmosphere, or of a discharge through the whole tree, with- , 

 out any apparent actual mechanical injury. 



If the stroke follows a vertical line along one side of the 



