CHAPTER XVII. 
DAMAGE TO TREES BY GASES. 
I 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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