1 PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. I. 331 



station, how the two systems encroach upon one another. At i8 h 25 m they almost entirely neutralise one 

 another's effect, at I9 h 5 there is a strong effect of the positive system, and at I9 h 25 a strong effect 

 of the negative system. 



The current-arrows at Pawlowsk and Christiania now seem to indicate, that this positive system 

 does not extend so far westwards. 



It is interesting to follow the movement of the arrow at Pawlowsk from I9 h 5 to I9 h 25, that 

 is to say, at the time the negative system is extending its area of precipitation westwards to Little Kar- 

 makul. The arrow at Pawlowsk moves with it. Thus, at I9 U 5 m the current-arrow indicates that the 

 station is more or less in the middle of an area of divergence somewhat to the west of the transverse 

 axis, so that we then have principally the effects of the positive system. At I9 h 25, on the other hand, 

 the current-arrow shows that the station is either in the east part of an area of divergence, or in the 

 west part of an area of convergence. This, then, indicates, that we here have either the effects of the 

 westerly positive system that we find in the neighbourhood of Bossekop, or those of the negative system 

 extending eastwards from Little Karmakul. It is probable, however, that both of these will exert an 

 influence, and that the current-arrow must be regarded as the result of their united action. 



The conditions here, are thus evidently governed by the polar systems, just as we supposed in 

 Part I. 



The direction of the deflections in the vertical intensity, are now, on the whole, the same as in the 

 preceding chart. We still find the same disagreement between Bossekop and Sodankyla; and at Paw- 

 lowsk P t = O, just as in the preceding chart. There is, howewer, a slight deviation in the curve, corre- 

 sponding to positive values of P,, which are too small to allow of being taken out. 



On Chart I' I and I'll, the conditions develope farther in the same direction, inasmuch as the areas 

 of precipitation are now concentrated more on the night-side of the earth, if we may judge by the 

 observations at our disposal. At the other polar stations, however, there are still, on the whole, more or 

 less distinct, westerly-directed current-arrows. 



It is very possible, however, that a little farther south there may be areas of precipitation that 

 cannot be observed here. The rather abnormal current-arrows at Fort Rae, which is situated south of 

 the auroral zone, might, perhaps, indicate something of the sort. On Chart VI too, Gottingen and Christiania 

 seem to be situated in the eastern part of an area of divergence, and thus indicate the ' existence of a 

 positive system of precipitation. 



We notice such a system at Bossekop and Sodankyla, and we should therefore have to suppose 

 that this system extended westwards along the auroral zone, and probably south of it, or into its south- 

 ernmost part, so that its effect at the stations from which we have observations, and which are situated 

 to the north of it, are not affected in any great degree by it. 



On Chart VII, the negative polar system in the north of Europe seems to have got the upper hand 

 and to be also governing the conditions in the stations in the south of Europe. As regards Christiania 

 and Gottingen, however, a positive polar system such as that we assumed to exist on Chart VI, will also 

 act in more or less the same direction. At Bossekop, up to 2i h 5 on Chart VII, there are marked 

 effects of a system such as this, although at the last hour shown, 2i b 20, this storm is over there. 



There is little to be said regarding the vertical intensities. At Fort Rae only, it may be remarked, 

 that there is now and again a deflection in a positive direction. This is in a kind of accordance with 

 the fact that the conditions of the current arrows are also slightly different from those at the other neigh- 

 bouring polar stations, which thus also seems to indicate that other perturbing forces are at work here. 



On Chart VIII, for the hours 2i h 40 and 22 h 4O m , the powerful storms at the stations here 

 under consideration, are over, although at several places there are sometimes quite powerful perturbing 

 forces; but there is now no distinct impression of a coherent current-system. 



