228 



and high-tension coil, the Lodge electrical valve, etc, while much 

 of the apparatus is protected by patents. 



By judicious arrangement the network of wire necessary to 

 charge twenty acres can be carried by some 20 poles. The insu- 

 lators have to be of a special type to prevent as far as possible 

 leakage down the pole, which is likely to occur in spite of the 

 fact that the charged wire never touches the insulator or pole, but 

 is fastened to it through the agency of yet another insulator and 

 a short piece of wire. 



Serious leakage in wet weathei and for some hours subsequent 

 to rain can probably never be prevented, but it is certain that, 

 with the devices now adopted by Mr Newman and with a new 

 form of insulator now in use at Evesham, given dry conditions, the 

 discharge takes place from the part of the overhead system intended 

 for the purpose. This discharge area consists simply of a series 

 of thinner wires stretched taut between two of the parallel thick 

 wires. With lower voltage it would probably be necessary to supply 

 downwardly directed points at intervals along the discharge wires, 

 but with this high voltage it is possible without this provision to 

 detect a quit? appreciable discharge from the wires when the ap- 

 para.tus is running properly. 



It is, of course, very necessary to have some simple method of 

 ascertaining that effective discharge is really occurring. 



The arrangement adopted is to have an insulated wire which 

 receives a charge when the overhead wire is giving off electricity, 

 and this charge can be detected quite simply, either by touching 

 the wire with the finger, when a slight sbock is felt as the current 

 passes through one's body to the earth. At night a different method 

 may be adopted; a vacuum tube, which will show a bright glow 

 as the slight current passes, may be used. 



Using this method it is possible to test to what extent the wires 

 are distributing the charge over the field, and hence at what dis- 

 tance apart they may be effectively put, a distance that varies with 

 height of crop and of the wires above the ground. 



It can also be shown that the treated area will not be sharply 

 delimited from the untreated if growing side by side, for it is found 

 that on wiudy days the discharge is carried considerably further over 

 the crop in the direction in which the wind is blowing. 



As it is possible by the method described to detect quite close 

 to the ground an appreciable discharge from a wire raised some 10-16 

 feet above it. it is clear that this height is preferable, as it permits 



