26 



Overhead Electrical Discharges. 



[APRIL, 



risk of a shock, which would be sufficiently violent to be a 

 considerable inconvenience. This result may be achieved 

 by running the electrical discharge only at night. At Bitton 

 this practice has usually been followed, the wires through 

 the greenhouses being charged at night and an area out of 

 doors electrified during the daytime; unfortunately there are 

 not sufficient physiological data to. hand to say whether 

 current applied at such a time is effective or not. If, how- 

 ever, it is desired to run the apparatus in the daytime, this 

 may quite easily be done, because the wires are so arranged 

 that, in those houses in which the doors open inwards, the 

 wire is attached to the door, and as the door opens the wire 

 sags until it reaches the ground and is thus discharged. 



The spark passing between the wire and the ground is 

 quite audible, and warns the person entering that if he closes 

 the door behind him he will be liable to receive a shock 

 from the wire, once more insulated and charged. In those 

 houses in which the door opens outward, Mr. Newman has 

 attached the wires to the door by means of a simple device, 

 which renders it impossible to open the door until the wire 

 has been slackened and lowered to the ground and thus 

 discharged. 



Apart from such additional problems as these, the question 

 of electrifying greenhouse crops is essentially similar in its 

 nature to that of treating areas out of doors, and this has 

 already been discussed. I only desire, in conclusion, to point 

 out one further difference that may be of great importance. 



In greenhouse work the plants are usually being forced 

 by the use of higher temperatures, and their physiological 

 functions must already be proceeding at a rate that is greater 

 than for plants in the open, and this may possibly have some 

 bearing upon the results produced by electrification. 



Can acceleration still be produced by the current, when vital 

 functions are already proceeding at a rapid pace ? 



The results previously referred to seem to answer in the 

 affirmative, but careful analysis of further results obtained 

 under glass is desirable before any definite statement is made. 

 Apart from this point, with work in the open in this country 

 it seems probable that temperature must so often be the factor 

 which limits the activity of plant processes, that when this 



