I 



CHAPTER XVII. 



DAMAGE TO TREES BY GASES. 



LLUMINATING gas is a frequent menace to the 

 street shade tree. Leaky gas-mains or service pipes are 

 common in town and city streets. The leak may come 

 from defective construction of the pipe-line or it may 

 result from the jars and jolts of traffic. The one thing of 

 real value is a policy of constant watchfulness to detect 

 trouble at the start, followed by immediate steps to 

 prevent its further progress and to overcome the damage 

 already done. 



This watchfulness must be exercised wherever a tree is 

 neighbor to a gas pipe. That it should be an immediate 

 neighbor in order for trouble to arise is not necessary, for 

 the damage may spread for a hundred feet or more from 

 the source of the leak. Frequently it is found that all 

 trees and other vegetation within this distance are affected 

 by the poisonous gas. The greatest injury is usually in the 

 section nearest the leak, of course, but serious harm may 

 be done at any point within the area through which the 

 escaping gas penetrates. 



The extent of the damage and the rapidity of the 

 spread of the gas depends on the size of the leak and the 

 character of the soil. When a pipe becomes broken and 

 permits the sudden flow of a considerable volume of gas, a 

 number of trees in the general neighborhood may be killed 

 within forty-eight hours. If the leak is small, such as 

 may be caused by the imperfect joining of pipes, or by the 

 separation of a joint, the spread is much less extensive and 

 the progress comparatively slow. Sandy soil permits the 

 gas to travel more rapidly and to extend through a greater 

 area than does clay. 



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