EXPERIMENTS 



When a branch or leaf-stalk is wounded or injured by being 

 tightly clamped in a vice, then it will be found that a 

 current of electricity passes from the injured spot to the 

 part that is untouched, and then in the reverse direction. 



Changes of current are also produced when a leaf is 

 suddenly exposed to light for a short time and then shaded. 



One of the most interesting observations is that made by 

 Major Squiers near Lorin Station, in America, where the 

 California Gas and Electric Corporation of San Francisco 

 has a long-distance transmission telegraph line. The power 

 is transmitted at a voltage of 56,000 with a frequency of 

 sixty cycles per second (three-phase). Major Squiers, from 

 previous experiments, thought that a note corresponding to 

 this frequency might be heard in a telephone receiver. The 

 following was the result : — 



" Upon connecting the telephone between two nails driven 

 in any growing tree along the route of the line, and at 

 a reasonable distance therefrom, the telephone responded to 

 this note with great clearness, and when the distance was not 

 more than 100 feet, the sound was very loud. For this 

 experiment no microphone need be used, nor any source of 

 electromotive force other than that induced in the tree itself, 

 the telephone being connected directly between two nails 

 driven into the tree. . . . 



"Several kinds of trees of various sizes and forms were 

 examined along this power transmission line, and all were 

 found to be singing with a loud voice the fundamental note 

 characteristic of the line current. Indeed, the strip of 

 vegetation along this line has thus been singing continuously, 

 day and night, for several years, since the operation of the 

 line began ; it needed only the electro-magnetic ear to make 

 the sound apparent. . . . 



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