408 
MR. W. R. CARR ON THE LAWS GOVERNING 
the various pressures are recorded in Columns V. and VI. of Table I., and the results 
are represented graphically in fig. 2a. 
In making these determinations, the precaution was always taken of allowing eight 
or ten minutes to Intervene between consecutive readings, in order to make certain 
that the air was in its normal condition when the discharge occurred. As can be 
seen from the figure, the curve is quite regular and exhibits all the peculiarities 
already noted by Peace,'-^ Strutt,! and Bouty.| The curve, however, is carried much 
higher than those drawn by any of these experimenters, discharges corresponding to 
potential differences of over 1800 volts being recorded. 
The distance between the electrodes was then varied and five difterent sets of 
readings were taken, in air, with the electrodes 1, 2, o, 5, and 10 millims. apart, 
respectively. The complete set of numbers for these different spark lengths is given 
in Table L, and curves showing tlie readings taken over that portion of the range of 
pressure below 5 millims. of mercury are exhibited in fig. 2 b. 
It is apparent from the relative positions of these curves in the figure, tliat at 
points at and below the critical jji’cssures, with a given potential difference ajDplied to 
the electrodes, the pressures at wliich discharges occuri-ed regularly decreased as the 
distance between the electrodes was increased. But a critical examination of the 
curves and also a reference to the numbers which they rei3resent show that 
Paschen’s law is rigidly applicable over the Avhole series of discharge potentials 
recorded. 
* Peace, ‘Roy. Soc. Proc.,’ vol. 52, p. Ill, 
t Strutt, ‘Phil. Trans.,’ A, vol. 193, p. 384. 
1 Bouty, ‘Compt. Rend.,’ vol. 131 (2), p. 44G. 
