PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. I. 375 



being due to the fact that the negative system, which there developes subsequently to such considerable 

 straight, is already encroaching upon the positive. In other respects there is little alteration in the 

 appearance of the field, and the forces at work are only sometimes weaker than before. 



The current-systems continue to develope upon the succeeding charts. On Chart IV, for the period 

 I5 h 40 to i5 h 50, the conditions are not very different from those on Chart III, except that the forces 

 at Fort Rae are a little more powerful. 



On Chart V the development of the negative system can be followed. At the first hour shown, 

 i6 h i5 m , Uglaamie is in its district of precipitation, but the latter does not extend as far west as 

 Ssagastyr. At i6 h 40, however, the great negative system has developed all round at the various 

 stations. This now forms a more or less continuous circuit, which can be traced from Godthaab to 

 Kingua Fjord, across Fort Rae, Uglaamie and Ssagastyr to Cape Thordsen and Fort Conger. 



The northerly position of this system on the afternoon-side is worthy of notice, as also its com- 

 paratively southerly position on the morning-side, as, judging from the vertical intensity, it should lie in 

 the first case to the north of Cape Thordsen, and in the second to the south of Fort Rae. 



We must, however, once more urge the necessity of caution in drawing conclusions from the con- 

 ditions in the vertical intensity, and need only point to the vertical arrows at Sodankyla during these 

 storms, which here too exhibit rather abnormal conditions as regards direction. 



The positive area of precipitation seems now to be considerably reduced, and distinct effects are 

 found only at Bossekop, Sodankyla and Little Karmakul. In reality, however, it may possibly extend 

 farther west, but then farther south than the regions from which we have observations. 



On Jan Mayen the current-arrow is comparatively very small, while the vertical arrow is of con- 

 siderable length and is directed upwards. This is in accordance with a circumstance that we have also 

 drawn attention to previously, namely, that the station is situated between a northern negative and a 

 southern positive system of precipitation. 



We find no special change in the form of the field in Charts VI and VII, but the forces increase 

 considerably everywhere. The high value of Pj. at Fort Conger should be especially noticed, it being 

 about 864 y at I7 h 2o m (Chart VII), or considerably more than any of the other perturbing forces observed. 



PI, cannot be measured at Uglaamie, as the needle has swung out of the field of observation; so it 

 may possibly have been as great or even greater here. It is interesting, however, to find that there is 

 also powerful precipitation close to the magnetic axis. 



As Charts VIII and IX show, the negative system encroaches farther upon the positive, and causes 

 a reversal of the current-arrow at Little Karmakul; while at the same time the current-arrows at Pawlowsk 

 and Kasan become more southerly in direction. On Chart IX, the effects of the positive system are 

 slight at the stations under consideration. 



At i8 h 20, on Chart X, we once more find a fairly powerful polar positive system of precipita- 

 tion from Kingua Fjord eastwards to Little Karmakul. This time, however, the system appears to be a 

 little farther north, at any rate in Europe; as Pawlowsk, Kasan and Gottingen are now distinctly in the 

 southern part of the area of divergence of the system. As this only lasts for a short time, it should 

 rather be regarded as a brief impulse. The effects of the negative system still continue, however, 

 although the forces are to some extent less powerful than before. 



Chart XI, for i8 h 55, represents the perturbation-conditions as they appear shortly before the 

 great systems disappear. We still find distinct traces of the great negative current-circle, while on the 

 other hand, the effects of the positive system are less distinct, although it seems to exist, judging from 

 the conditions in Jan Mayen and the southern stations; but this cannot be decided with certainty. 



When these storms have ended, there is an interval of more or less normal conditions at most 

 places, although it is by no means quiet everywhere; but what perturbations there are, are of a more 



