PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. I. 39 1 



The most powerful storm does not develope, however, until this first phase is past. 



The second phase of the storms in this second section may be considered as coming in the interval 

 between 2O h 40 and the close of the period. The deflections, which at first, at any rate, correspond 

 to the effects of a negative polar storm, are very powerful everywhere; and at Uglaamie and Ssagastyr 

 the needle passes out of the field of observation. The various deflections, however, are not so well- 

 defined as to make it easy to find any distinct movement of the systems. 



What we will, however, draw particular attention to, is the perturbation-conditions at Fort Rae. 

 At the close of the period, a distinct change takes place there in the direction of the perturbing force. 

 We previously found only negative deflections in the horizontal intensity, indicating that negative 

 systems of precipitation were at work; but now a positive system appears here. That this station is on 

 the afternoon-side of the globe, and further that it is to the south of the auroral zone, are circum- 

 stances that agree closely with what we should have expected to find; and the positive system, the 

 existence of which, during the last storms, we were unable to prove, and could only suggest the possibility 

 of, appears once more just at a time when we might expect to find its effects at the stations we are 

 considering. 



At the southern stations the forces are unusually powerful. 



The fields of force for this last phase of the storms, will be found represented on the last three 

 charts, from 2o h 5o m to 23 h i5 m . 



We now find, as so often before during the powerful storms, a negative current-circle round the 

 geographical pole. 



The greatest forces are found upon the night-side, and they are of unusual magnitude. The 

 storms are negative everywhere, except at 22 b 2o m and 23** i5 m in America, where we meet with the 

 effects of the already-mentioned positive storm. In Europe, the negative area of precipitation has moved 

 farther south, if we may judge by the conditions in the vertical intensity; for both in Jan Mayen and 

 at Cape Thordsen there are now positive values of P,, whereas previously they were negative only. 

 The precipitation seems therefore, now to take place to the south of these stations, whereas, previously it 

 was chiefly to the north. This is in agreement with the fact that the negative area of precipitation comes 

 farther south on the night-side than on the day-side 



In Europe, the direction of the current-arrows is rather south, even as far north as Bossekop. In 

 Central Europe this is the normal condition during similar storms; but the forces there are now so 

 powerful, that to a certain extent we have used the same scale as at the polar stations. 



On Chart VII, the powerful negative storm is almost over, and only at a few places we now find 

 perturbing forces, indicating that it is still in existence. At Fort Rae, on the other hand, we find 

 powerful effects of the positive storm that has been mentioned as occurring there. 



