Feb. 15, 1872] 



NATURE 



303 



A VIEW of the magnificent aurora of Feb. 4 was much interrupted 

 here by great masses of cloud, which frequently drifted over 

 large tracts of the illuminated sky, and towards 8 o'clock col- 

 lected and descended in a general downpour of rain. Neverthe- 

 less enough of it was seen to produce a very striking impression. 

 It began to tinge the southern sky at a considerable altitude so 

 early in the evening that I thought it must have been the reflec- 

 tion of a crimson sunset ; nor was I undeceived till T had been 

 to the other side of the house, where I found the western horizon 

 glowing with amber light, in which was no trace of the expected 

 ruddiness. Red continued throughout to be the prevailing hue, 

 chiefly in great diffused masses, but occasionally broken up into 

 filaments and streamers ; there twas, however, no absence of 

 sheets and columns of the more usual pale green light. The 

 clouds, chiefly heavy cumuli, assumed a stranije aspect ; some- 

 times, when opposite to the crimson illumination, reflecting a 

 dull and sombre red, at others, when projected in front of it and 

 enlightened from the other side by the twilight, or the green 

 aurora, standing out in' lurid and ghastly contrast. At one period 

 the northern part of the sky, up to a great altitude, though clear 

 and studded with stars, appeared at first sight almost like a black 

 cloud from its contrast to the greenish white sheet which 

 bordered it abruptly at a considerable height on the west ; this 

 again passing into crimson masses in the south, and sending out 

 a whitish stream to meet another from the east, and form, pro- 

 bably, for a few moments, a complete bright ring, somewhat 

 south of the zenith, of which, however, only one half could be seen 

 from the post of observation. The light was so intense that even 

 after it had been a good deal obscured by cloud, a large print 

 might have been read without much difficulty. A mmiature 

 spectroscope (one of Browning's) brought out some interesting 

 features. The usual yellowish green auroral line was distinct 

 everywhere, and could be perceived even when the instrument 

 was directed to masses of dense cloud ; and as was observed by 

 Birmingham on a former occasion, could be made out in the re- 

 flection from any suitable terrestrial object ; white paper for 

 e.'iample exhibited it very obviously. As shown in the brighter 

 greenish patches in the sky, it remained visible even when the 

 slit was so much contracted that the sodium band of a common 

 fire would have been thinned down almost to its smallest breadth 

 before extinction. Such a diminution of light, however, was fatal 

 to the rest of the spectrum, which was a very remarkable one. 

 With a wider slit a crimson band, bearing a fair amount of con- 

 traction, was perceptible in the brighter patches of that hue, 

 with a dark interval between it and the principal green band. On 

 the opposite side of that green band, beyond a second similar 

 dark space, was a i5onsiderable extent of greenish or bluish light, 

 quite decided, but so feeble as to leave it undecided whether it 

 was of uniform brightness, or (as I suspected) compounded of 

 contiguous bands ; beyond this again was another dark space, 

 leading on to a faintly luminous band, too dim to show colour, 

 but which must have taken its place somewhere in the blue. 

 This band, and the darkness adjacent to it on the less refrangible 

 side, were each about as broad as the intensely vivid yellowish 

 green stripe. Could the light have borne sufficient reduction, 

 we should certainly have had three narrow bright bands in the 

 red, green, and blue, the two latter being wide apart, with either 

 a faint separate continuous spectrum, through part of the inter- 

 val, or pos^jibly several feeble lines, which the vridening of the 

 slit fused into one lengthened area. 



The peculiarity, first noted I believe by Otto Struve, was 

 very obvious, that even where the naked eye recognised the 

 strongest and fullest crimson without a trace of green, the green- 

 ish yellow band in the spectroscope far exceeded, perhaps three 

 or four times, the red line in visibility. This display was dis- 

 tinguished from almost all that I can recollect to have witnessed 

 through many years, by its very feeble development in all the 

 northern portion of the sky. 



Hardwick Vicarage, Hay T. W. Webb 



Will you kindly permit me to correct an error which crept 

 into my letter of last Monday on the aurora. The words 

 "western" and "north-eastern" in the 14th line should have 

 read respectively "eastern'' and " north-western." Allow me 

 also to call attention to the present condition of Jupiter. On 

 Thursday evening List the eq latorial ochre-tinted belt was lighter 

 in colour than 1 have seen it of late year.o, but much and di>- 

 tinctly mottled with light and dark clouding, two dark hanging 

 s;ioti on the upper edge, with adjoining elliptical bright patches, 



being conspicuous, while the lower dark madder-brown edge was 

 very unequal, being swollen and thick about one-third to the 

 rigtit from the centre, and thinning off towards each end. The 

 dark belt above the equatorial zone had two knots or thickenings 

 of considerable size upon it, and the whole series of belts pre- 

 sented ragged and dentated edges, and, to use the apt phrase of 

 a lady who saw them, had a "mountainous " look. 



On occasional glimpses I more than suspected a general 

 mottling of the whole surface of the planet, which, moreover, 

 presented a dull appearance, the dark and light belts and spaces 

 not being, as I thought, so well contrasted as usual. The poles 

 were coloured as in ordinary, the upper one warm and ochreish, 

 the lower slate grey. The instrument used was Browning's 8 \ 

 reflector, full aperture, with inserting achromatic eye-piece 306. 

 A transit of a satellite and its shadow added to the general effect. 



Guildown, Guildford, Feb. 10 J. R. Capron 



O.v Sunday, the 4th of February, at 10 p.m., I observed the 

 central point of the "corona" of the aurora visible that even- 

 ing to be situated between 1, 64 and 65 Geminorum, in R. A. 

 7h. 20m. and N. decl. 28'. Our latitude is N. 50" 50' 55", and 

 longitude E. 0° 32' 50". 



The "corona" drifted away very slowly towards the E. 

 against a slight E. wind blowing at the time. 



Perhaps some of your contributors can calculate the aurora's 

 height from the earth from the above notes, and let us know the 

 result through your journal. J. E. H. P. 



St. Leonard's, Sussex, Feb. 12 



Not wishing to trouble you with a long description of the 

 aurora observed by so many on the evening of the 4th, I will 

 confine myself to a few remarks. The spectrum of the brighter 

 portions, viewed through a five-prism direct instrument, con- 

 sisted generally of the four lines mentioned by Captain Maclear; 

 but when the spectroscope was turned towards the brightest of 

 the curved streamers forming that splendid red and pink star, 

 which so suddenly burst forth at 7'25, some degrees south of the 

 zenith, the relative intensity of the lines was completely changed, 

 the red line becoming more strongly marked even than the 

 green. 



The fact that the green line can always be detected, even 

 where the unassisted eye fails to notice any trace of auroral light, 

 might suggest the advisability of a daily observation with a small 

 hand spectroscope for those who are desirous of forming a com- 

 plete list of all auroral phenomena. Magnetic disturbances are 

 a sure guide in the case of grand manifestations of aurora ; but 

 might not a very slight aurora be observable without the magnets 

 being sensibly affected ? 



On the evening of the 4th the magnetic storm commenced 

 about 2 P.M., and was at its height from 4 to 9, though the 

 magnets were not steady again until after sunrise the next 

 morning. S. J. Perry 



Stonyhurst Observatory 



I WRITE a very short account of the great aurora of February 

 4, as seen by me in the south-east of France, between Chambery 

 and Macon. It may be of some interest, as a brilliant aurora is 

 very unusual in those latitudes, and this was quite comparable in 

 brilliancy to the auroras of October 1870, and November 1S71, 

 which I witnessed in Scotland. The sunset was very clear and 

 bright, but as the sunlight gradually faded, light fleecy clouds 

 appeared in difi'erent parts of the sky, with the ruddy tints cha- 

 racteristic of the Northern Lights. As it became darker the red- 

 ness increased in intensity andextent, overspreading a large portion 

 of the sky, especially towards the zenith, and was streaked with 

 bands of greenish white light. On the eastern horizon a well- 

 defined arch of this pale green light was visible for some time, 

 while underneath the arch the sky was so black that but for a 

 large star shining in the centre of the blackness, I should have 

 supposed that the darkness was due to a heavy cloud. There 

 were, in fact, no true clouds at the time in the sky, and the large 

 stars were everywhere visible amid the shifting masses of nebulous 

 light, which at one instant seemed to be the ruddy reflecti.m of 

 a great fire, and at another to be lighted up by the rays of a full 

 moon. Long streamers of red and green light seened to shoot 

 up towards the zenith from almost every point of the horizon at 

 various times ; but singularly enough there appeared to be lewer 

 displays of this sort in the north than in any other quarter of 

 the heavens. Being, however, in ^ railway carriage in motion, 



