116 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1934 



rate of decay of the polonium, additional collectors were fitted sym- 

 metrically to the boom throughout the year so that the rate of 

 pick-up of potential remained not less than a safe limit. The control 

 measurements of the potential gradient were made over a level 

 stretch of rock using the Simpson stretched wire method. Twice a 

 day whenever possible, at 9 h. and 15 h. local time, measure- 

 ments were made of the air-earth current, using a Wilson guard- 

 ring electrometer modified to incorporate a Lindemann electrometer, 

 and of small ion content of the air by an Ebert aspiration electrom- 

 eter, also modified by Mr. Sheppard. On almost all days while 

 these measurements were being made the number of Aitken nuclei in 

 the atmosphere were counted by an Aitken counter. During the 

 spring months series of experiments were made over periods of 24 

 hours to determine the nature of the diurnal variation of the air- 

 earth current, ion content, and Aitken nuclei, as well as of the rate 

 of production of ions near the ground. 



Though some of Mr. Morgan's meteorological instruments had 

 been functioning continuously from July 1, it was nearer August 

 before the magnetographs had settled down in their new quarters, 

 but by the first of that month, the zero hour for the general Polar 

 Year operations, all was in working order. 



Since by that time the evenings were fast drawing in, we set 

 about finding a means of maintaining communication between our 

 main base and the substation, the site of the 1882-83 activities, 

 15 miles down the lake to the southeast. For a fourth and impor- 

 tant item in our program was the simultaneous photography of 

 suitable types of aurora at two ends of a base-line, to allow the 

 height and orientation of the aurora to be measured from the ap- 

 parent displacement of the same piece of aurora against its stellar 

 background on pairs of synchronously exposed plates. To have the 

 two-way communication which is almost necessary for this work, 

 we had taken a supply of Silmalec wire made for us by the British 

 Aluminum Co., and specially insulated by Henleys Cables, Limited. 

 In its final form the wire weighed only about 23 pounds per mile. 

 This we hoped to erect down the lakeside between the two stations, 

 using the spruce and birch trees for support. But on detailed recon- 

 naissance the shore was found to be so broken and irregular that to 

 have followed the shore would have exceeded our length of cable, 

 if not also our amateurish capabilities in erection of telephone lines. 

 So we decided to wait till the lake had just frozen and in the mean- 

 time, that is between August and October, we used two small wire- 

 less transmitting and receiving sets. Though the simultaneous photo- 

 graphic work could, in default of other means of communication, 

 have proceeded by this means with difficulties and inconveniences and 

 probably much loss of effective aurora, we started to erect the tele- 



