90 MR. GEORGE C. SIMPSON ON THE 



detect the emanation with certainty, and none yielded more than a 100 | 000 part of 

 what the same quantity of pitchblende would give on heating." Thus the soil 

 conditions of Karasjok do not appear to be abnormal, so that the high radio-activity 

 found there during the winter must be due to the meteorological conditions being so 

 favourable to the collection of the emanation in the lower atmosphere. 



In order to compare the value of the radio-activity at Karasjok with that of other 

 places, the only observations which can be used are ELSTER and GEITEL'S,* in 

 Wolfenbiittel (mid-Germany), and GOCKEL'S,! in Freiburg (Switzerland) ; no other 

 observer has extended his observations over a sufficiently long period to give good 

 mean values. Neither ELSTER and GEITEL nor GOCKEL observed between 8 P.M. 

 and 8 A.M., and as the values I found between those hours were very much the 

 largest it is not right to compare my means with their means, so in what follows 

 I use only the values which were obtained during the morning and afternoon 

 observations in Karasjok. 



The means for the whole year are Wolfenbiittel 18 '6, Freiburg 84 and Karasjok 60. 

 Thus Freiburg is the highest and Wolfenbiittel the lowest. The absolute maxima 

 (between 8 A.M. and 8 P.M.) are Wolfenbiittel 64, Freiburg 420, Karasjok 384, i.e., 

 the same order as before. 



It is a strange fact that the yearly period should be so marked in Karasjok, while 

 no yearly period can be detected in either Wolfenbiittel or Freiburg. As stated 

 above, neither ELSTER and GEITEL nor GOCKEL have observed after 8 P.M., so it is 

 impossible to compare the daily periods. It would be exceedingly interesting to 

 know if there is a large daily variation in mid-Europe, for if there is not, then the 

 mean winter value of the radio-activity in Karasjok will be very high compared with 

 mid-Europe, the mean for the winter, when night as well as day observations are 

 taken into account, being 126 at Karasjok. 



GOCKEL'S maximum observation of 420 was quite an exception, but even that was 

 exceeded by my absolute maximum of 432 (observed between 8 and 10 P.M. on 

 December 17). With this one exception the values found by GOCKEL did not 

 exceed 170, while I found 200 quite a medium value during the winter in Karasjok. 

 It would appear, from the results which have already been published, that high 

 values of the radio-activity are much more common in Karasjok than in any place 

 yet investigated. 



ELSTER and GEITEL measured the radio-activity at Juist, an island in the North 

 Sea, and found it only 6, while in the Bavarian Alps they found the high value 

 of 137. From this, and their observations in Wolfenbiittel, they concluded that the 

 radio-activity increased from the sea inland. In order to find if the same conditions 

 held in the north, I stayed in Hammerfest on my way home, and made daily observa- 



* ' Phys. Zeit.,' 4, p. 526, 1903. 

 t ' Phys. Zeit,,' 5, p. 591, 1904. 



