' PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPKRIMKNTS. CHAP. I. 363 



At Little Karmakul there seems moreover to be a positive system of precipitation. But it is 

 especially interesting here to find the positive system of precipitation in the vicinity of Fort Rae, as this 

 is the only station in this district situated to the south of the auroral zone, and where therefore one 

 would expect to find effects of a positive system, if such a system actually existed in those regions. 

 This is the first instance we have of a storm, which appears at Fort Rae at this time of day, and it 

 thus proves to have the character of a positive polar storm. This instance is of peculiar interest, as it 

 shows that the occurrence of positive afternoon storms, which we have so often demonstrated at the 

 European stations, as also at Ssagastyr during the storms just described, is also found in these regions. 

 The reason why opportunities of observing this phenomenon here are comparatively rare is probably 

 principally that this is the only American station in a suitable position a little south of the auroral zone. 



The perturbation-conditions at Sodankyla are also interesting. The horizontal forces are compara- 

 tively very small, indicating that this station is not far oft the point of convergence of the negative 

 system, a circumstance which is immediately evident on looking at the charts. 



If we consider the vertical perturbing forces, we see in the negative area of precipitation, that at 

 the two polar stations, Cape Thordsen and Jan Mayen, which are to the north of the auroral zone, there 

 are perturbing forces directed downwards; while at the two polar stations, Little Karmakul and Bossekop, 

 which are to the south of the auroral zone, the forces are directed upwards. This seems clearly to 

 prove that the precipitation takes place more or less exactly in the auroral zone. 



With regard to the vertical forces at Sodankyla, the conditions are just as abnormal as in the 

 previous perturbations. The forces are positive and fairly powerful. Concerning them, we will only 

 refer the reader to the remarks previously made about this condition. At the southern stations there are 

 well defined perturbations in the various elements, simultaneously with the negative storm in the north. 



Seven charts have been drawn for this perturbation. On the first three, we instantly recognise the 

 principal phenomenon that was the characteristic one in this storm, namely, the strong negative area of 

 precipitation on the night-side of the globe in the regions around Northern Europe. South of the area 

 of precipitation, a very distinct area of convergence is formed, with all its characteristic peculiarities. 

 The vertical intensity at Sodankyla is the only exception. In order to obtain a better impression of this 

 area of convergence, we have also drawn a current-arrow on Charts II and III for Kasan. From 

 this station, we have five-minutely observations in declination, but in horizontal intensity only readings 

 at an average interval of two hours. At about 23'" 5o m , Gr. M. T., we find a reading, which, when 

 compared with the other readings, shows with tolerable certainty that at that time there is a perturbing 

 force PI, of about -f- I 5J / - -As we had drawn no chart for this hour, we have employed this value 

 together with the two values of P^, which can be determined directly for the two points of time. The 

 two current-arrows are thus only to be regarded as an approximately correct expression for the respec- 

 tive perturbing forces; and they have only been included here in order to bring out more distinctly the 

 form of the area of convergence. 



On the other side of the principal axis in the system of precipitation, one would expect to find an 

 area of divergence; but during the preceding storms, the conditions in these high latitudes have been so 

 perturbed that it has been impossible to prove the existence of anything of the kind. This time, however, 

 the area of precipitation is so local that we might perhaps expect to find it. 



We do moreover actually find perturbing forces at Kingua Fjord and Godthaab, which, in strength 

 and direction, are very much what we should expect to find in that part of the area of divergence, 

 which comes into these districts. 



At Fort Conger, there are only small perturbing forces in the declination. If the point of diver- 

 gence of the system were between this station and Cape Thordsen, the direction of the current here 



