Fan. 25, 1883 | 
NATURE 
2 
97 
by many of the German and Dutch astronomers; but as 
it seems little known in England, though referred to 
by Mr. Rand Capron on p. 64 of his beautiful work, 
“Aurore.” In this theory most of the properties of 
aurorz are deduced from cosmic dust entering into the 
atmosphere of the earth. I take the liberty to direct 
attention to the unexpected argument, that the brilliant 
object of November 17, 1882, has brought forth in favour 
of my “‘ Théorie Cosmique,” to which I had already the 
opportunity to refer in this Journal in my article “On 
Dust, Fogs, and Clouds” (vol. xxiii. p. 195). 
Furthermore, I think that this object is not the only 
example of such a phenomenon. On November 2, 1871, 
there was seen in Groningen and several places of 
Germany a strange, brilliant arch, striped parallel to its 
well defined sides and changing its curve during its two 
hours of existence. The beginning of the phenomenon 
(of which I gave a description in the Dutch journal /szs) 
was seen by a student, Mr. Gratama, like an elliptic 
patch of light round the Pleiades. Dr. Vogel, who ob- 
served the same arch at Bothkamp, determined its auroral 
character by the spectrum, Otherwise it resembled 
very much the bright spur of a gigantic meteor or fireball. 
Also it disappeared slowly, beginning at the east end, 
as the illustration shows. A faint aurora, with dark 
segment, was visible in the north. The height of this 
arch was calculated by me approximately at 127 kilo- 
metres or 79 miles. I think that the only difference 
between these two feather-like phenomena of November 2, 
1871, and of November 17, 1882, consisted in the different 
apparent velocity and in the greater mass of meteoric 
dust, forming in the case of November 17, 1882, but a 
short, and in that of November 2, 1871, a very long train 
of incandescent matter. It must be remembered here 
Auroral Arch, observed November 
that the tails of great fireballs remain visible for half an 
hour or more (see e.g. the article of Mr. Branfill, vol. 
XXVil. p. 149). In NATURE, vol. xii. p. 330, is to be 
found a description of similar arches, seen at Fremantle 
in Australia by Mr. Lefroy, in presence of the moon, 
which was obscured by one of them. 
This leads us to a question, touched by Mr. Back- 
house, NATURE, vol. xxvii. p. 198, that of the halos seen 
in Siberia (by Von Wrangel, I believe), when an auroral 
beam was in front of the moon. I watched in vain if such 
an event should perhaps occur November 17 last, but Mr. 
Zeeman, whom I have cited above, seems to have been 
so happy as to have seen a white and bright auroral 
cloud floating over the moon’s disc at 5h. 47 (local time), 
giving the common interference phenomena. It is un- 
necessary to remark, that these phenomena can be 
formed by all kinds of dust, formed of nearly equal 
2, 
1871, at Groningen (Netherlands), 
| particles, and that they in no way require ice-par- 
| ticles. On my inquiry why the observer could decide 
that it was not a common cloud, be brought forward the 
| following arguments :—(1) Its great brightness; (2) its 
| transparency to the starlight; (3) its very great velocity, 
| unusual in common clouds. 
Returning to the meteoric phenomena, visible simul- 
taneously with aurore, it seems that such phenomena 
were seen during the marvellous aurora of January 
7, 1831, described in Poggendorf7’s Annalen of the same 
year. We read (p. 440) that Bergrath Senff, in Colberg, 
at 6.30 o’clock, saw above the west horizon a bright 
| yellow streak, rising upward with a common cloud- 
| velocity, passing at 30° N. Zen. D., and forming an arch 
| from W. to E,, beginning to disappear from the west end, 
| almost at the same moment that it reached the east 
| horizon. At p. 458 we see that Prof. Rudberg, at Upsala, 
