
(rene? 5 
XXV.—On the Disruptive Discharge of Electricity. By ALEXANDER 
MAaAcFARLANE, D.Sc., and P. M. Piayratr, M.A. 
( Read 1st July 1878.) 
During the months of May and June of this session we have endeavoured 
to investigate certain questions suggested by our experience of the discharge 
of electricity through the gases and through oil of turpentine,* for which 
purpose Dr Macrar.ane had received a grant from the Royal Society of 
London. 
Discharge through Liquid Dielectrics. 
When paraffin oil (the kind employed for illuminating purposes) was put 
into a glass vessel, in which were two brass plates arranged in the form of a 
condenser, and when the plates were charged by means of the Holtz machine, 
it exhibited the same phenomena as oil of turpentine. Gas bubbles were 
produced ; they did not appear until after the passage of the spark. Once 
produced, they facilitated the passage of the spark through bringing the electrified 
surfaces virtually. nearer to one another. Hence, when taking observations of 
the difference of potential required to pass a spark through layers of different 
thickness of the oil, it was always necessary to remove the bubbles generated 
by the passage of one spark before electrifying again. This was effected by 
bringing the discs into contact. 
The axis of the bubble in the direction of the lines of force was observed to 
‘become elongated before discharge. When the charge was positive, the 
bubbles were attracted to one surface; and when negative, to the other. 
They were generally attracted to the positive surface, but sometimes to the 
negative. We have not been able to detect the condition on which this 
difference of behaviour depends. In the case of oil of turpentine, the attrac- 
tion was always to the negative plate. The attraction was more marked when 
no jars were on the conductors of the Holtz machine. The gas liberated is 
a hydrocarbon, and there is a deposition of carbon simultaneously. 
* “On the Disruptive Discharge of Electricity,’ by Auex. Macraruanz, M.A., B.Sc., “Trans. 
| RS.E,” vol. xxviii. p. 633; and “On the Discharge of Electricity through Oil of Turpentine,” by 
the same author and R. J. S. Smupson, “ Trans. R.S.E.,” vol. xxviii. p. 673. 
VOL. XXVIII. PART II. 8 0 
