extremities to the top of the tree, or practically a distance of 3 ft. 



A sunflower seedling, 17 in. high, and 3-16 in. in diameter, gave 

 a resistance of 25000 ohms for i in. of stem, and 3 in. of the root, 

 while a slightly larger plant of the same species gave 7500 ohms, for 

 I in. of stem, and ^ in. of moist soil. 



THE EFFECTS OF ALTERNATING CURRENTS. 



The voltage and current of alternating sys- 

 tems employed for lighting purposes are much 

 greater than those utilized by street railways, 

 and the cases of burning of trees by alternating 

 currents are probably more numerous than 

 those produced by direct currents, for the 

 reason that a larger number of these wires are 

 in the tree belt. Some alternating feed wires 

 in use carry enormous currents. The higher 

 the current a wire carries, the more dangerous 

 it is to trees, for insulation in such cases is 

 less effective and hence arises more leakage 

 and a greater possibility of burning. Accord- 

 ing to our observations, the effects of alternat- 

 ing currents on trees are local, that is, they 

 produce injury only near the point of contact. 

 This results in the death of that portion of the 

 tree where the burning occurs, and if it is a 

 leader or a large limb it frequently has to be 

 sacrificed, much to the detriment of the tree. 

 A portion of a tree below the point of contact 

 is frequently affected, the extent of injury 

 varying with the electrical potential of the wire, 

 etc. In no instance, to our knowledge, has the 

 alternating current caused the complete death 

 of trees. It may, however, burn and disfigure 

 young trees so badly that it practically 

 amounts to complete destruction. The alter- 

 nating current is, however, capable of killing 



plants, as we have frequently demonstrated in 



Fig. 4, Showing the 1 1 . -.i ^ r u 



effects of electrical ^^^ laboratory, with a current from a no volt 



burning and strangu- system. The current necessary, however, to 

 accomplish this, generated considerable heat. 



