6l2 ISIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 1902 1903. 



"My records, however, will show that there is a regularity of appearance and the closing off of 

 these pulsations, which proves that they do not belong to so uncertain a cause as atmospheric changes 

 but to the nebulous substance itself. They seem to intimate a great internal commotion in the nebulous 

 matter, for they were too rapid to be occasioned by irregularities in its exterior surface. 



"I noticed them again the following year, but must refer the reader to my records and charts. 

 The changes were a swelling out, laterally and upwards, of the zodiacal light, with an increase of bright- 

 ness in the light itself; then in a few minutes, a shrinking back of the boundaries, and a dimming of the 

 light; the latter to such a degree as to appear, at times, as if it was quite dying away; and so back 

 and forth for about three quarters of an hour; and then a change still higher upwards, to more perma- 

 nent bounds". (Observations of the zodiacal light by JONES, vol. 3 of the Report on the United States 

 Japan Expedition, 1856, page XIII). 



The pulsations of the zodiacal light thus recorded cause one involuntarily to think of the regular, 

 often almost sinusoidal magnetic pulsations and simultaneous oscillating earth-currents which so frequently 

 occur, and markedly in the month of March. (See Part III of this Section.) 



As an example, I shall quote an observation of JONES, not, it is true, from March, but from the 

 evening of the 3Oth January, 1854, "The pulsations of the zodiacal light were very distinct". At the 

 end of his series of observations we find: "7 h 54, its boundaries had risen to b again and .... bright: 

 7 U 55 at a ar) d very dim: 7 h 56 at b, and bright: 7 h 57 at a, and very dim: 7 h 58^ at b and 

 bright: 7 h 59^ m still at b and bright: it seemed now to be permanent at b". 



Here we have plainly a period of about 2 minutes. 



From another observation of JONES: "These lateral changes of the whole body of the stronger 

 zodiacal light are very remarkable. I cannot see any room for mistake, as there might have been, had 

 the light been more inclined to the horizon. But the horizon and ecliptic made nearly a right angle". 



For comparison I shall adduce that, at the Haldde observatory, in March, 1900, I observed beautiful 

 magnetic oscillations with a period of 128 seconds. 



In May, 1910, I again registered at Kaafjord beautiful magnetic waves and simultaneous earth- 

 current oscillations of very nearly 119 seconds, as will be seen in the subsequent part of this volume. 



I quite perceive that it is easy to imagine that what are called magnetic elementary waves, which 

 have specially been studied by ESCHENHAGEN, have their origin in oscillations of electric ray masses. 



It may be worth mentioning in connection with this, that the earth in March and September is at 

 the farthest possible distance from the nodes of the sun's equator. 



It appears to me very probable, in view of the properties above described, that the zodiacal light 

 must be primarily occasioned by electrical phen6mena. 



We shall now further analyse the most important attributes that the zodiacal light has been ob- 

 served to possess, and see if they can be put together and explained by the supposition of an emana- 

 tion of corpuscular rays from the sun. The question whether the axis of the zodiacal light is situated 

 in the ecliptic or in the equator of the sun has been carefully considered in two important treatises by 

 ARTHUR SEARLE. In the first of these, "The Zodiacal Light" (Proceedings of the American Academy of 

 Arts and Sciences, 1883) as well as in the second, "The Apparent Position of the Zodiacal Light", 1885, 

 he has made extensive researches by making special use of numerous observations from the classic and 

 admirable volume by JONES. 



In the following pages I shall endeavour to interpret all the results of observations with which I 

 am acquainted, by starting with the supposition to which I shall subsequently come, in order to explain 

 the diurnal variation and the origin of terrestrial magnetism, viz: that the corpuscle-rays continually radiate 

 from the sun's surface (see Section I, p. 314). But these continuous rays must be assumed to possess 

 properties somewhat different to those of the very stiff corpuscle-rays that radiate in short periods from 

 the sun-spots, and which, we supposed, specially occasioned magnetic storms on the earth. 



