468 
NATURE 
[April 13, 1871 

The Spectra of Aurora and Corona 
So much attention has been drawn to the correspondence be- 
tween the spectrum of the corona and that of the aurora, as to 
lead one to suppose that they were almost identical ; or, at 
least, that the principal auroral line was also seen in the corona. 
But even this is notat all the case. As the readers of NATURE 
are aware, the light of the aurora is almost monochromatic, 
giving a spectrum of one bright line in the yellowish green (wave- 
length about 557), and three or four very faint bands, which are 
more refrangible. These last are only occasionally visible, and 
indeed, Angstrom, in 1869, had seen them but once, and that 
momentarily. It is with one of these faint bands that the 1,474 
corona line (wave length 531°6) is said to coincide, and not with 
the bright line (wave length 557), which is entirely absent in the 
corona spectrum. Two more of the auroral bands are near to 
the F and G hydrogen lines, which are visible in the corona, but 
it is yet doubtful whether they coincide. It is not impossible that 
a faint H spectrum may be produced in the aurora by the moisture 
of the air, but I incline to attribute them to the low temperature 
air spectrum mentioned in my letter of February 7, and which 
has bands in nearly the same positions. From the extreme faint- 
ness of the auroral bands, it is of course impossible to measure 
their positions with great accuracy. 
Under these circumstances it would seem rather premature to 
lay great weight on the supposed coincidence, and much careful 
work must be done both on gas spectra and on that of the aurora 
before we can say with any confidence that these lines are not 
due to gases already known to us under different circumstances 
of temperature and density. 
I subjoin a table, giving the approximate wave lengths of the 
lines observed in the auroral and coronal spectra. 

Lines of Corona and 
“ Observers. 
Prominences. 
Lines of Aurora. 





Description| Wave length) Description | Wav clength 
C Hydrogen 656 
Bright line. {630 H. R. Procter and 
1640* others, 
D Sodium 589 
b; 
t 5560°7. | Angstrém 
Bright line. {537 Winlock 
560t plan Clarke, jun. 
; 531 Winlock 
1474 line 530'6 band eee Alvan Clarke, jun. 
E 527 
band 520 Winlock 
b 517 } 
¥ Hydrogen 486 band 485 Alvan Clarke, jun. 
band 464 Winlock 
G Hydrogen! 435 band 434 Alvan Clarke, jun. 

HENRY R. PROCTER 
Royal Colleze of Chemistry, March 28 

The Aurora 
THE splendid aurora which was visible here last night was 
probably seen in many other places, and from a comparison of 
data, perhaps the position of the luminous arch, which formed 
a conspicuous part of it as seen from here, may be made out. 
At 10.30 it passed through the northern part of Corona, 12 
Canum Venaticorum, and the head of Leo. At the time men- 
tioned above, the whole of the light was a vivid green, but at 
about 10.40 red patches appeared, and at 10.45 rays shot up toa 
point situated about 4° S.S.W. of 12 Canum. The colour round 
this point was a most wonderfully dark blood red, and in many 
other parts of the heavens the same colour was seen, very different 
from the rosy light of last October. 
About 11 clouds coming up covered the whole sky, and on 
their partially clearing away, the aurora was much decreased in 
brilliancy. The lurid red light reflected from the detached clouds 
which preceded the main body produced an exceedingly grand 
effect. The light was strong enough to read type of the size in 
which NaTuRE is printed. 
On first observing the green parts with a spectroscope of one 
bisulphide prism, the only line distinctly visible was the green 
one ; but by watching and opening the slit there came into view 
two bands at the more refrangible end, more sharply defined at 
the more refrangible side than at the other, and there also seemed 
* Seen on October 26 last year, but very rarely visible. 
+ Prof. Pickering considers this an error. My own measures give a 
wave length very slightly greater than those of Winlock and Angstrém. 

to be a considerable continuous spectrum from the green line 
nearly to the least refrangible of the two bands. 
In the red parts the red line was most brilliant, quite equal in 
intensity to the green one, and then even in the green light it was 
distinguishable with care and long watching. 
York, April 10 T. Ti. WALLER 

Last evening, at about 9.50, my attention was called to a 
magnificent display of aurora borealis. A mass of light, com- 
posed of red and bluish-white streamers er rays, moved rapidly 
up from about W.S.W. to E.N.E., and the whole took the form 
of an arch overhanging fora short space of time the western 
horizon, while transverse waves of light, intensifying the lustre 
of the blue portions, and occasionally reaching almost to the 
zenith, rolled across the nebulous mass at intervals of about a 
second. 
great brilliancy, like sheet lightning, except that they were sepa- 
rated by a sharp line from the dark surrounding sky. Each flash 
made a fresh advance eastwards, like the skirmishers preceding 
an army, and a few bright crimson clouds alone kept nearly the 
same position throughout the display,—the finest of these was 
nearly in the S.W. At one time, when the flashes and waves had 
ceased, an umbrella-like radiation of red and white rays from the 
zenith attained great beauty. By five minutes past ten the sky 
had regained a more ordinary hue, but dull red clouds still 
remained, and in the west a white phosphorescence like early 
dawn. The night was calm and rather cold ; the barometer 30°00 
and steady. The wind had been gusty from E. in the afternoon. 
I had remarked during the daytime some very rare and beautiful 
modifications of cirrus and wave-cloud stretching from W.S. W. 
to E.N.E. (a direction coinciding with that of the aurora 
streamers), and crossed by bars at right angles to them at a lower 
elevation. The arrangement of these clouds showed that they 
were strongly acted on by electricity, as is generally, perhaps, 
the case with wave-cloud. May not vapours of this kind 
in a peculiar state produce the apparent polarisation of 
the sun’s rays recorded by ‘‘J. W.” in the Zimes of April 8? 
To-day, especially, between’ twelve and one o’clock, detached 
cumuli, driving rapidly from about E.S.E. and upper cirro- 
cumuli from E.N.E., have behaved in a manner quite unlike 
anything I have observed before. The only cirro-cumulus to be 
seen in the morning shot out branches in advancing and melted 
away between the branches, leaving a sort of skeleton of spine 
and ribs, which in their turn were dissipated. The cumulus 
motions were also unusual, for portions were suddenly arrested, 
remaining fixed, and then rose apparently and arranged them- 
selves in bands more or less parallel until dissolved. The last 
phenomena only occurred, as far as I could see, below some 
whitish rays, extending across the sky from W.S.W. toE.N.E., 
parallel to the aurora streamers of last evening, and closely re- 
sembling the beams of light which often proceed from the sun 
when behind a cloud on a showery day. Either an aurora must 
be going on to-day, or the higher atmosphere is in a peculiar 
electrical state. The influence of these whitish bands on the 
clouds at a much lower level is at any rate remarkably powerful. 
Wrexham, Denbighshire, April 10 
Solar Science at the pleasure of Secret Referees 
In the faithfully-recording columns of Nature for March 30, 
at p. 434, is a much required abstract of Mr. Stone’s important 
paper, recently communicated by him to the Royal Society, 
London, on the connection between terrestrial temperature and — 
sun-spot phenomena. By comparing the curves of mean annual 
temperatures during the last thirty years (as observed, ready to 
his hand,by his indefatigable predecessor Sir Thomas Maclear) 
with another curve constructed on Wolf’s observations of sun- 
spots, Mr. Stone has been enabled to deduce, almost immediately 
after arriving on his new scene of labour at the Cape of Good 
Hope, first, that there is an approximately decennial period of 
such temperature, and so similar to that of the sun-spots as to 
indicate more than a mere coincidence ; and secondly, that the 
sun-spots are not to be looked on as the direct ages of thent 
temperature variation, but that either phenomenon results from 
some general change of solar energy. 
As Mr. Stone expressly mentions ‘‘ that he had not the slight- 
est expectation, on first laying down the curves, of any sensible 
agreement resulting,” I presume that he is not aware that 
upwards of a year ago I beth sought the honour and experienced 
¢ 
Streamers projecting eastwards kept shooting out with. 
