Death in such cases resembles that 

 from heat, as the maximum death 

 temperature is quite similar in each 

 case. The collapse of the plant in 

 such cases is due to the heat gener- 

 ated, rather than to an electrical 

 shock, inasmuch as it is possible to 

 pass the same current through 

 plants, under conditions where heat 

 is not generated, without causing 

 any damage to the tissues. It is 

 generally believed that the arc light 

 is injurious to trees. We have never 

 been able to discover any injuries 

 resulting from the use of the arc 

 light, and we have observed hun- 

 dreds of cases where the light was 

 in close proximity to trees. Many 

 plants will die, or linger along in a 

 sickly condition, if subject to poor 



soil conditions, and given an insuf- 

 Fig. 5. Showing deep burning ' 



of a large limb, caused 'by an alter- ficient supply of food material. 

 nating wire of high potential. Such cases of death however, 

 From Luke Doogue, City Forestry 



Dept., Boston. should not be attributed to the sup- 



posed injurious effects of the elec- 

 tric light. 



EFFECTS OF DIRECT CURRENTS. 



Most of the direct currents that trees have to contend with are 

 those generated in operating electric railroads. The electro motive 

 force generally employed on these circuits is about 500 volts. The 

 feed wire not infrequently passes through the tree belt, and occasion- 

 ally it comes into contact with the limbs of the trees. Although the 

 voltage and current are less on this system than on the lighting sys- 

 tem, electrical injuries are likely to prove fully as disastrous. The 

 great majority of burns resulting from the direct current are similar 

 to those produced by the alternating current, namely, they are largely 

 local, that is, the burning predominates close to the point of contact 

 with the wires. The feed wires cause no burning to the tree when 



