521 



The apparatus not being self recording, it was of course impossible to obtain anything approaching a 

 continuous record of the variations of the potential. An unbroken series of hourly observations was 

 obtained extending over the three days from 8 a.m., November 22, to 8 a.m., November 25, 1902. These 

 were taken at the ordinary position on shore at a height of five feet above the ground. A further series, 

 in this case of 2-hourly observations, also extending over three days (noon, October 7, to noon, 

 October 10, 1903), was also obtained. These were taken at the same place, but with the match at a height 

 of 1 2 feet above the ground. A varying number of observations were taken daily throughout the rest of 

 the time, except on days when observing was rendered impossible by blizzards. During the middle of the 

 second winter, between May 8 and August 19, 1903, no observations were attempted owing to shortage of 

 the supply of electrometer matches. 



The difficulty and discomfort inseparable from meteorological observations in circumpolar regions are 

 accentuated in the case of measurements made with the portable electrometer, owing to the fact that the 

 instrument is not direct reading, the divided head having to be adjusted to bring the cross hair to its 

 " sighted " or zero position. When the observations had to be taken with the aid of artificial light the 

 difficulty must have been greatly increased. It is not surprising, therefore, that the number of 

 observations per day was reduced in the winter months, and that continuous series of hourly observations 

 extending over a day or more are lacking for these months. 



RESULTS. 



The more striking features which appear on an examination of the values obtained for the potential at 

 the place of observation will be considered first. In what follows, the times throughout are mean local 

 times. 



1. SIGN OF THE POTENTIAL. 



The potential was almost invariably positive, as in temperate latitudes. Only on 11 days were negative 

 values met with. Particulars of these occasions are given in the table which follows : 



In lower latitudes the occurrence of negative potentials is generally associated with precipitation. On 

 only three of the days of the above table (October 27, 1902, and January 13 and 14, 1903) was there 

 precipitation. On most of the days the sky was overcast for part of the day at least, but March 4, 1902, 

 and February 13, 1903, were fine and clear nearly all day. 



2. INTENSITY OF THE NOKMAI. ELECTRIC FIELD. 



The mean potential gradient under normal weather conditions is about 60 volts per metre (or about 40 

 volts per metre if the original constant of the instrument lie used). It has of course to be borne in mind 

 that, as pointed out above, the deformation of the eqnipotential surfaces by observer and apparatus may 



3 X 



