DISRUPTIVE DISCHARGE OF ELECTRICITY. | 641 
is then no term independent of s; and the coefficient of s, it may be observed, 
‘ b , 
is somewhat greater than the ~ of the equation 
V =43'190 ./{s? + 13690s}. 
It thus appears that by heating the discs the cause of the existence of the 
term independent of s has been removed. Now, heating the discs removes 
condensed gas. The curvature involved in the parabola must be due to a 
decrease of temperature, as also to the increase of distance between the 
discs. 
Table XIV. (fig. 12) contains the investigation for air under the same 
conditions. The results are precisely similar. The ratio of the coefficients of 
the equation for hydrogen is 4:17, while that of the coefficients of the equation 
for air is 4°45. The coefficient of s is somewhat greater than the a of the 
equation 
V =66°940 / {s’ + ‘20503s} . 
Their ratio is 1°30, while for hydrogen the ratio is 1:25. The investigation 
of Table XIII. (fig. 11) is the same as that of Table XIV., excepting that in 
heating the discs the air inside the receiver was also heated ; whereas, in the 
case of Table XIV., only the discs were heated, a difference, in my opinion, 
sufficient to account for the difference in the magnitude of the coefficients. 
During this series of observations special notice was taken of the place where 
the spark passed. c denotes that it was at the centre, and nc that it was near 
the centre. 
In Table XV. are observations undertaken to test whether a change in the 
capacity of the charged conductor has any effect upon the readings. The 
couple of small Leyden jars referred to are those usually hung on the conduc- 
tors of the Holtz; they were always on when measurements were made, 
excepting in the case of Table XVIII. The capacity of the large jar when 
tested was found to be five times that of the couple of small jars. If the three 
last readings for the large jars are more correct than their predecessors, it 
would appear that the change of capacity has no effect upon the reading. But 
the difference of the curves of Tables XVII. and XVIII., if not otherwise 
explicable, supports the opposite conclusion. 
Table X VI.—By “continued discharge,” is meant a discharge which kept 
the spot of light at a fixed deflection. This deflection was always less than 
that for the corresponding single discharge. The image can be made to 
remain very steady with only a slight oscillation. The zero was more dis- 
_ placed than in the case of the single spark, owing probably to the greater 
VOL. XXVIII. PART II. 8 D 
