2 4 



Overhead Electrical Discharges. [april, 



electrical discharge, the influence machine, with, however, 

 the attendant disadvantages of smaller output and liability 

 to interruption owing to the unsuitability of most forms of 

 influence machines for continuous running, or (2) to adopt 

 the high-tension system described for work in the open. 



Along the first lines ran the early experiments at Mr. 

 Newman's nurseries at Bitton, and with remarkably good 

 results on the whole, the occasional failure being probably to 

 be attributed to causes which could easily be controlled. If 

 anyone is desirous of attempting this method, any friend 

 conversant with electricity, and in particular with influence 

 machines, could probably supply the necessary information 

 for installing such an apparatus. Experience would soon 

 show the most practicable method of working, precautions 

 being taken, as suggested in the previous section, to see that 

 an effective discharge is being obtained. 



In my own experiments with plants growing under glass 

 under wires charged from an influence machine, I have 

 always found it necessary, to ensure a good discharge, to 

 have downwardly directeH points, formed of the free ends of 

 short lengths of fine wire twisted around the stouter wire 

 carrying the charge. 



In applying the other method in use at Evesham to work 

 under glass, several points had to be considered. The main 

 difficulty was the great tendency to leakage under these 

 conditions, and in practice it was never possible to keep 

 up such a high charge on the wires running through the 

 greenhouse, as, with the same apparatus, could be obtained 

 in the open field. At the same time it was quite possible 

 to keep up an effective discharge, Mr. Newman and myself 

 testing the point on several occasions by carrying a long test 

 wire into the houses and testing the distribution of the charge- 

 To avoid leakage where the current entered the house, a 

 pent roof was put up to prevent the water dripping on to 

 the insulators used, and under this pent roof was placed, 

 first a large porous cylinder or perhaps an ebonite tube, and 

 within this a tube of fused silica, some two feet long, through 

 which the charged wire (gutta-percha covered wire) ran, 

 These fused quartz or silica tubes are easily obtainable now- 

 adays, and seem the most satisfactory type of insulator. 



