ATMOSPHEKIC ELECTRICITY IN HIH LATITUDES. 63 



4. To measure the amount of radio-active emanation in the atmosphere. 



5. To investigate as far as possible the influence of the Aurora on the 



electrical conditions of the atmosphere. 



In my choice of a station I decided to get as far north as possible without being 

 actually on the sea coast, and found that the Lapp village of Karasjok (69 17' N., 

 25 35' E., 129 metres above sea-level) was very wfll suited for my purpose. 



Meteorological Conditions. 



Before going on to a discussion of the electrical results obtained, it will be as well 

 to give a short account of the meteorological conditions experienced during the year's 

 work. From its high latitude the north of Norway should be a very cold district ; 

 but the presence of the open ocean on the north and West greatly modifies the 

 temperature. The effect of the water is of course very much more marked on the 

 sea coast than inland. As one recedes from the coast the mean temperature for the 

 winter six months falls very rapidly, it being 2'3 C. at Gjesvoer, near the North 

 Cape, and 11'7 at Karasjok. If there were no interchange of air between the ocean 

 and the interior of the land the latter would of course have a very low temperature. 

 This became very noticeable during periods of calm weather, for the temperature 

 would then run down to very low values, reaching on several occasions 40 ('., 

 while, on the contrary, whenever the wind rose the temperature rose also. 



When there was no wind, a cap of very cold air would form over the land, causing a 

 nearly permanent temperature inversion. Although 1 could not observe this inversion 

 instrumentally neither kites nor balloons forming part of my equipment there could 

 be little doubt as to its reality. On September 3()th, with an air-temperature of 

 G C., a bright rainbow was observed. Then again, on descending the high banks 

 of the river, one felt at once the cold air collected in the river basin, and the Lapps 

 stated that it was seldom as cold on the hills as in the valleys. Then, again, the fact 

 that a wind was always accompanied by mild weather also points to the cold of still 

 weather being confined to a laver of air of no considerable depth lying over the surface. 

 This condition of things almost entirely prevented the formation of ascending currents 

 of air, so causing very small values of the amount of precipitation and almost entirely 

 preventing the formation of low clouds during the winter. It also had a very marked 

 effect on the electrical condition of the atmosphere, to which reference will be made 

 later. 



During the summer the weather conditions were very similar to those of England, 

 with the exception that the precipitation was very much less and thunderstorms were 

 scarce. On three days only was thunder heard and lightning was not seen once. 



From November 26 to January 18 the sun did not rise above the horizon; never- 

 theless, even in the darkest days there were two or three hours of twilight during 

 which the sky was too bright for the stars to be seen. The period during which the 

 sun did not go below the horizon extended from May 20 to July 22. 



