^4 HIKKKI AND. II IK NOKWKC ,l.\.\ Al'KOKA 1'OI.AKI.-, KXI'I-.IH I 1OX , I QO2 1903. 



after which the negative storm acts exclusively, at the last two stations, we find here too a considerable 

 difference in time between them, namelv, of almost e.xactlv one hour. 



Thus the negative storm appears considerably later at the more westerlv stations than to the east, 

 in thi> district; and wo feel justified in taking these circumstances as a proof that the negative storm- 

 centre in this section of the perturbations, is moving westwards, and thus in some wav or other is fol- 

 lowing the sun in its apparent diurnal motion. 



It would not be right, however, to draw conclusions respecting the details of this movement from 

 these facts, tor it cannot, of course, be taken for granted that the district of precipitation moves exactly 

 along the auroral /.one as the perturbations run their course. This is all the more inadmissible from 

 the fact that at Cape Thordscn and Fort Conger, there arc distinct proofs that also polar arc-as qf 

 precipitation exist farther north, and that therefore- in detail the conditions may be a little more com- 

 plicated. It would at anv rate be natural to expect that the conditions would not be so simple if, instead 

 of comparing stations that were all situated south of the auroral /.one as was the case with the three 

 stations just considered we were to compare the conditions at stations lying some to the north and some 

 to the south of that /one. This proves to be the case, when we go farther west to Jan Maven, and 

 compare the conditions there with those, for instance, at Bossekop. There too, it is true, there is first 

 a positive storm, which is very powerful and pronounced, and later on the direction of the deflections 

 in the horizontal-intensity curve change, indicating that now, instead of a positive polar storm, the 

 effects are those of a negative storm ; but the change takes place earlier than at the more easterly situ- 

 ated Bossekop. The cause of this may therefore naturally be looked for in the circumstance that Jan 

 Maven is situated to the north, and Bossekop to the south, of the auroral /one, and that therefore the 

 northern, or north-western, branch of the negative district of precipitation -if it may so be called might 

 be supposed to reach |an Maven earlier than its eastern, or more southern part reaches Bossekop. The 

 explanation of the conditions in Ian Maven might thus be that it was the effect of the negative system 

 of precipitation at Cape Thordsen, extending, as the perturbation proceeded, westwards to Jan Mayen, 

 or possibly moving in that direction. This view is further supported by the fact that the change in Jan 

 Mayen occurs just at the time when there is a sudden, very considerable increase in the negative deflec- 

 tion in the horizontal-intensity curve lor Cape Thordsen. When we finally come to consider the con- 

 ditions of the vertical intensity, we shall return to this subject with other circumstances that favour 

 our view. 



1 he negative deflections in the horizontal-intensity curve for Jan Mayen are comparatively small. 

 In the declination, on the other hand, there is n uniformly-directed, westerly deflection, which, as a 

 rule, exceeds those in the horizontal intensity in strength. About the time when the change in the 

 horizontal intensity takes place, there is no special change to be observed in the deflections in the 

 vertical intensity or the declination. 



It is possible, perhaps probable, that here too, after the change has taken place, there are still 

 effects of the positive system. The comparatively small forces in the horizontal intensity, and the 

 comparatively powerful forces in the declination, seem to indicate something of the kind; but it is 

 difficult, indeed impossible, to settle the point with certainty. 



The other station where there were distinct effects of the positive system of precipitation was Godt- 

 haab. Here the system acts a trifle longer than in Jan Mayen; but there is no negative storm after- 

 wards, the conditions being fairly normal. 



With regard to the southern stations, we see that the conditions in the horizontal intensity, during 

 the first part of the section, are rather variable. At those lying more to the west, such as Christiania 

 and Gtittingen, however, there- are throughout perturbing forces that act in a negative direction, and are 

 of sufficient magnitude- to indicate, more or less certainly, an area of divergence which should answer to 



