Electricity Radium-, N-, and X-rays 



These experiments are of course distinctly encourag- 

 ing, but whether the cost of producing even a 50 per 

 cent, increase of the crop will prove economical or not, 

 is a question which can only be solved by many trials. 



There is also the danger of electrocution. In America, 

 strong electric currents are used to destroy the railway 

 weeds (see p. 258). Continuous electric currents for 

 street cars have also been found to destroy trees, 

 especially in wet weather. Alternating currents seem 

 to stimulate the growth of trees, but this is sometimes 

 injurious. 3 



In America, where long distance transmission lines of 

 high voltage are common enough, secondary induction 

 currents must often be set up in any trees which happen 

 to be growing close to the wires. That this is really 

 the case seems certain from Major Squiers' experiment. 

 He found that on attaching a telephone to the trunk of 

 any tree within a hundred yards of such a line, a distinct 

 note could be heard due to the induced current. These 

 trees had been "singing" the same note without any 

 rest for years ever since the line had been built.* 



When an electric discharge is passed through ordinary 

 air, both nitrogen and hydrogen are affected, nitrous 

 and nitric acid are formed, and also peroxide of hydrogen. 

 It is probably these substances which are responsible 

 for the destruction of bacteria, 5 but ozone is also pro- 

 duced, which is again a bactericide. Ozone affects yeast 

 injuriously, and also those ferments or enzymes which 

 play an important part in every physiological process in 

 plant life. 6 



Pollacci has suggested that the process of assimilation 

 depends upon electrical currents in the leaves, and it is, 

 as we have seen, a fact that peroxide of hydrogen is really 

 formed by electric discharges in the atmosphere. 7 

 * See "Romance of Plant Life," p. 198. 

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