43 



time, when the leakage is more or less extensive, the odor of the soil 

 becomes extremely obnoxious. This odor disappears very quickly 

 when the soil is aerated, and when a gas leak is repaired it is an ex- 

 cellent idea to leave the ditch open for a few days to get rid of the 

 strong odors which are present in the soil. There is a certain ca- 

 pacity for adaptation in plants to poisons, which probably exists to 



some extent in the case of trees 

 affected by gas, but this capacity is 

 limited, and if the leakage of gas is 

 continuous the roots are sure to 

 be poisoned in time. It requires a 

 considerable amount of gas to 

 kill a large tree, but it must be 

 borne in mind that the conditions 

 surrounding a tree are favorable 

 for maintaining gas in the soil for a 

 long time. Certain devices may be 

 employed at no great expense when 

 installing a system of lines which 

 will readily detect sources of leak- 

 age and prevent gas escaping into 

 the soil, thus preventing injury to 

 trees. There are many instances 

 where the cutting of roots under a 

 roadbed, which is necessitated by 

 regrading and placing curbing, has 

 saved trees from injury from gas 

 poisoning, and the presence of con- 

 duits near leaks has been known to 

 prevent injury to many trees. 

 If symptoms of gas poisoning are discovered in only one root, and 

 the poisoning has not extended to the tree trunk, amputation of the 

 root is the best remedy. 



Fig. 23. Showing burning caused by 

 alternating current wire. 



