Feb. 8, 1872] 



NATURE 



283 



sides the blue and violet, saw Angstrom's green aurora' line per- 

 petually over cirron acetylene at \V. L. 5579, and the red aurora 

 line between sodium a and lithium a, but nearer to the latter, 

 say at \V, L. 63^0. 



3. Now, W.L. 6350 in the solar spectrum is a pretty brieht 

 scarlet red, so that orange could easily be made of it by the green 

 aurora mixing therewith, and the spectroscope separates each of 

 the two kinds of light with perfect ease But how came potassium 

 red or W.L. 7700, ?'.t'., the blood red, lurid red, and tragedy red of 

 painters to appeir so markedly to the naked eye, and yet not be 

 seen at all in the spectroscope, either as a new ingredient or sn 

 alt'^red place of the red line ? It would apparen'ly be by the 

 mixing up of rays and streamers of th^: blackness out of that l'>ng, 

 low dnrk arch on the northern horizon. But when a spectroscope 

 fails (as fail it must) to show a characteristic line for a region of 

 blackness, what other instrument can we take to prove the case ? 



Exressively f.iint greenish and bluish lines appeared at wave 

 lengths 5300, 5100 and 4900 nearly ; but the mam light in the 

 spectroscope was to the extent of S-tenths of the whole, ttiat of the 

 green line 5579, and of I 7-tenths the red line 6350 ; whi'e to 

 the naked eye the splendour of the display and its variety con- 

 sisted in triple mixtures of 5579. 6350, and ihe unknown dark 

 melium. Could something be a^c-rtained about that, if those 

 who have good te'escnpic star spectroscopes were to observe a 

 star when shilling through one of these inky black arches ? 



At 9.30 P.M. when all the auro-ahad faded orp'ssed awayto- 

 wardsthe>outh, whereafew stragjling pink patches siill appeared, 

 the northern horiz m and its sky being now free from the black 

 arch, as well as the green stremiets, p-rfectly asioni-;hed me by 

 the clear pellucid biue of a true starlight night sky in a bright 

 Climate and clear atmosphere. Evidently the dark arch and 

 streamers a'-e as much a part of the aurora as the g een .and red 

 lights, but how to investigate them — that is the question. 



C. PiAZZi Smyth 



15, Royal Terrace, Edinburgh, Feb. 5 



Last evening an aurora of rather unusual brilliancy was seen 

 here. I happened to he out with a friend in the ccmntry about 

 sunset, when the sky was comoletely overcast and fine rain was 

 falling. We noticed that darkness did not coone on so quick as 

 usual, and at 7 o'clock it was so light as to lead my frimd to 

 believe tha' the moon was shining above the clouds. Later in 

 the evening slight breaks began to appear in the clouds, through 

 which the first magnitude stars were just visible, and through thrse 

 openings an in^en^e red illumination appeared. The spectroscope 

 gave from every part of the heavens a very bright line in the 

 green, and another fainter one nearer the blue, together with a 

 diffused light over the green and blue parts of the spectrum. 

 The brightest part of the aurora was towards the S.W. From 

 the large amount of light, although it was raining at the time, it 

 must have been one of the brightest auroras that have been 

 witnessed for years. G. M. Seabroke 



Rugby, Feb. 5 



Coming up the Channel on Sunday night last in the P. and O. 

 screw-steamer Delta, about 9.40 P.M., I saw a very fine aurora. 

 The sky was cloudy, which somewhat dimmed its brightness, but 

 it was rather brilliant towards the N. 



Having a Hoffman's direct vision spectroscope with me, I 

 turned it towards the brightest red portion which'lay towards the 

 N. E., and with a moderate slit got a very sharp and distinct line 

 in Ihe green at or near the position of F in the solar spectrum. 

 No other lines were viNible. But on removing the telescope, 

 and observing the spectrum with the naked eye, a fine crimson 

 line revealed itself near C ; the colour of it was exactly that of 

 hydrogen a, as seen in a vacuum tube. 



I also thought that there were faint traces of structure visible 

 in the blue and violet, but of this I cannot be sure. 



There had been traces of auroral phenomena visible early in 

 the same evening. The green line was so distinct that unpractised 

 observers saw it easily. The red line, however, was much 

 fainter, and appeared to flicker. 



I much regret that I had no means of recording the position 

 of the lines. R. J. Friswell 



About six o'clock on Sunday evening the ruddy appearance 

 of the upper clouds gave warning of an aurora in prospect, but 

 J v,T.5 not prepared for the magnificent sight which appeared on 



looking out an hour later. The higher part of the sky seemed 

 covered with bright rose-coloured clouds, which, from the dark 

 masses of cl"uds passing underneath, seemed continually to be 

 shifing in position. Intervals of deep gi'een appeared a'nongst 

 the red, and these, when looked at with a spectroscope, gave a 

 stronger light than their surroundings. Objects near were illu- 

 minated as if the moon had risen behind the clouds. I had a 

 miniature spectroscope of Browning's, with which I examined 

 the brightest parts, and obtained four lines — one very bright 

 green, two very faint nebulous green bands, and one red line. 

 Having a spirit lamp handy, in which were remnants of sodium, 

 lithium, and sulphate of copper, I was able roughlv to estimate the 

 positions of the lines. The red was about a third from D towards 

 the li'hium line; the very bright green about -.i third from D to the 

 copper line near b, the other faint green hands were more refran- 

 gible, and I should think their places were between b and F, and 

 near F, hut I could not get th-ir positions so well as the other 

 two ; cr-rtainly the most refrangibl-* was not so far as the violet- 

 potassium line v/hich I could see in the field. 



The light green w.as present everywhere, the red only showed 

 orcasinnally with vcy varying intensity, and the most refr-mgible 

 green line was also continually varying, but it was brighter than 

 the se ond green line. 



Th"^ ight around attained its maximum about a quarter to 

 eight, aiiH then very slowly dimini-ihed to about midnight, when 

 it had nearly disappeared. A light drizzling rain was falling the 

 whole time. J. P. Maclear 



Shanklin, Feb. 5 



Thrive has been a mignificent red aurora here this evening. 

 I saw it first bef ire twilight had quite disappeared, and a' first 

 thought it was the cimson of sunset unusuall/ late. It was at 

 its finest between six and .seven ; at that tim'; there were columns 

 of light shooting up from the horizon abnost to the zenith, and 

 o:ciinying almo-t half the horizon from the E. of N. Mund 

 by E. The crimson colour wsis variegated with b'uish white 

 in a way that I have n it seen hef ire The b.irometer was at 

 about 29 '45 inches, with a stro.ig breeze from the sou h. 



J'isi-:ph John Murphy 



Old Forge, Dunmurry, Co. Antrim, Feb. 4 



There was a fine display of aurora here yesterday evening. 

 I fir-t observed it about 5. 30, just in the twilight, but it was then 

 confused with the r.ays of the setting sun ; as the darkness 

 deepened the aurora came out alone, and was then extremely 

 beautiful. It extended from the extreme N. E. to the extreme 

 N. \V., but from the reflection of the numerous clouds, appeared 

 to have a much larger area. It was of a bright crimson colour, 

 with the rays golden or orange, of which, however, only a very 

 few were visible. 



As the evening came on, about 8 o, the clouds gradually 

 became thicker, and at last almost entirely covered the sky ; the 

 only effect then apparent was a deep red glow, which continued 

 with unequal intensity until II 45 and with all probability much 

 later. At 9.35 there was a break in the clouds towards the E., 

 when the aurora shone forth in all its splendour. The aurora 

 was most certainly visible in daylight, just appearing as the twi- 

 light came on. 



I have no doubt if the .atmosphere had been clearer, we should 

 have had a most magnificent display ; a,s it was, the effect was 

 really brautiful. J. S. H. 



Gloucester, Feb. 5 



There has been a magnificent and extensive auroral display 

 this evening, of which I beg to send you the following account. 



After a very heavy fall of rain, which lasted in this part of the 

 country from I o'clock p.m. until 5 30 o'clock, there were col- 

 lected in the northern horizon numerous cinv-slyatus clouds, 

 which gradually at first, and afterwards rapidly, moved towards 

 the E. , with the strata to the S. As these were pas-ing 

 away. I saw, about midway between these clouds and the zenith 

 a bright patch of pile red light, which became well defined by 6 

 o'clock. A few minutes aft^r this appeared I saw in the N. W. 

 another patch of red lii;ht, and bv b. 15 there stretched from N., 

 N.W., and N.E. three vey broad streamers converging in the 

 zenith, and forming a splen.^id crimson canopy, the streamers 

 being quite separated, until meeting, by dark spaces. These slowly 

 disappeared, and of a sudden there appeared a bluish-white 

 streamer stretching N.E. to and passing the zenith by about 10°. 



