PART II. POLAR MAGNETIC PHENOMENA AND TERREI.I.A EXPERIMENTS. CHAP. I. 339 



Afterwards, four areas of precipitation should be found, distributed over the polar regions. Owing 

 to the scarcity of stations, it is of course difficult, if not impossible, to prove any agreement in detail. 

 We will only point out that on Chart III, the perturbing forces are distributed more or less evenly 

 about the auroral zone. 



At the conclusion the negative storms are concentrated upon the night and morning side, perhaps 

 moved a little more towards the night-side than one would expect. On the afternoon-side there are no 

 particularly powerful areas of precipitation, but we have no observations either, from the regions south 

 of the auroral zone. 



While speaking of the repetition of the phenomena in reverse order after the sun has crossed the 

 meridian of the magnetic axis, we will draw attention to the two deflections in the horizontal-intensity 

 curve at Uglaamie, which seem distinctly to be almost a repetition of the same phenomenon. The second 

 phenomenon does not, it is true, occur when the sun is exactly as far west of the meridian of the mag- 

 netic axis as it was east in the first, but only approximately so. 



If this phenomenon is to be explained in this manner, it must be assumed that as, at the first 

 deflection, the station lay to the west of the storm-centre, and as the strength of the deflections is more 

 or less the same, at the second deflection the station must be almost equally far to the east of the 

 storm-centre; and it is very probable that this is the case. 



Similar remarks may also be made with reference to Fort Rae. 



THE PERTURBATIONS OF THE 2nd JANUARY, J883. . 



(PI. XXV.) 



84. The perturbation-conditions on the above day exhibit in many respects a great resemblance 

 to the conditions during the preceding perturbation of the I5th January, 1883. This is at once evident 

 on comparing the plates for these two days. 



The period of this day which we shall discuss is from u 1 ' to the conclusion of the day, 23'' 20, 

 Gr. M. T. 



During this period there occur, as on the i5th January, a series of powerful, well-defined storms, 

 while for some time previously, it had been more or less calm. 



On this occasion also, the perturbations occurring may be divided fairly distinctly into two sections, 

 namely, a first section from n 1 ' to i6 h , and a second section from i6 h to 23 h 2o m . 



The first section is mainly characterised by the powerful negative storms that appear in North 

 America. 



At Fort Rae, there is a considerable and well-defined deflection in the horizontal-intensity curve, 

 with a corresponding deflection in the declination curve. The deflections increase at first fairly 

 evenly from u h 3o m . We find the most powerful perturbing forces at about I4 h ; after which the forces 

 decrease, until about 15*' 3o m , when the conditions are again more or less normal. 



At Uglaamie, the conditions are somewhat more complicated. At a little before I2 h , wide de- 

 flections suddenly' occur in the magnetic curves. In the horizontal intensity, they are in a negative 

 direction, and the curve has a very jagged appearance. At about i3 h , however, they decrease, and 

 for a time the curve oscillates over and under the normal line. In the declination, on the other hand, 

 the deflections at this hour are very considerable, showing the presence of powerful perturbing forces, 

 which are evidently acting in the neighbourhood of this station. 



Later on there are again considerable negative deflections in the horizontal-intensity curve, these 

 deflections now being very well-defined without any sharply projecting points. The}' continue to the 

 end of the first section, the conditions at about I5 b 45 being once more normal. 



