74 ROYAI, SOCIETY OF CANADA 
At no time was a negative potential observed and only on a couple 
of occasions did the potential fall to zero. 
On October 7th, 1908, with temperature ranging between zero 
and 7 above, and accompanied by a light S.E. breeze and with the air 
full of snow particles, a potential of over 800 volts per metre was re- 
corded for a period of two hours from 10.30 a.m. to 12.30 p.m. 
During the winter months, owing to the extreme cold, great diffi- 
culty was experienced in keeping the electroscope insulated and also 
in keeping the flame of the collector burning, and as a result, very 
few records were obtained. 
In the months of May and June records were obtained simultan- 
eously with the two instruments whenever conditions would permit, 
and these records cover observations on each hour of the 24, from 
which the following empirical formule have been deduced by the 
method of Fourier series. 
1. For potential gradient— 
y = 95.5 — 14.7 cos 8 + 12.5 cos 20 + 5.8 cos 30 + .... 
+ 0.5 sin 9 — 4.4 sin 20 — 5.6 sin 36 + .. 
where y is the potential expressed in volts per metre 
and @ is time expressed in degrees at rate of 1 hour to 15 degrees, and 
beginning at 0 hours, midnight. 
2. For conductivity of the air— 
y = 2.818 + .154 cos 6 — .031 cos 29 — .072 cos 30 + .... 
+ .363 sin 0 — .547 sin 26 + .144 sin 30 + .... 
where y = x x 10“ 
and @ is time expressed in degrees at rate of 1 hour to 15 degrees, and 
beginning at 0 hours, midnight. 
An abstract of the simultaneous observations is given in table 3, 
in which q is the ratio of positive to negative dispersion. 
