Feb. lo, 1881 



NATURE 



349 



j^eneral tendency of tlie movement being an increase of westerly 

 declination and of vertical force, whilst the horizontal force 

 slig;htly diminished. Quicker movements of the needles com- 

 menced at 3.40 p.m. Greenwich mean time, and from that hour 

 until ii.'ii p.m. oscillations followed each other at short inter- 

 vals, although the magnets at no time appeared to be in the 

 state of rapid vibration they were in during the afternoon of 

 August 12. 



The principal deviations registered were as follows : — A large 

 westerly deflection of the needle was recorded at 6.2 p.m., but 

 the greatest excursion in that direction took place at 6.47 p.m. ; 

 at 7-12 p.m. there was also another considerable westerly move- 

 ment, followed by an easterly, which reached its maximum at 

 7. 48 p.m. At 8.18 p.m. it deviated ag.iin to the west, after 

 which it returned to its approximately normal position at 8. 33 

 .p.m. An isolated deflection to the west at about 0.25 a.m. of 

 February i wound up the storm. 



As regards force, the greatest changes of horizontal force 

 occurred at about 6 ]3. m., but they were not large in extent. 

 The vertical force curve moved in the extent of an .nugmented 

 force beyond the limits of registration of the instrument between 

 4.20 and 5.32 p.m., and again between 6.2 and 6.45 p.m. The 

 greatest movement in the direction of diminished force was at 

 8.12 p.m. 



The self-registering Thomson electrometer was not apparently 

 affected by the aurora ; the tension of atmospheric electricity 

 being somewhat high positive at 9 a.m., fell to a low positive 

 tension at 2 p.m., from which it rose gradually, although some- 

 what irregularly, until 8 p.m. ; from that hour until 9 p.m. it 

 was more disturbed ; it then became more strongly positive, and 

 remained so until the next day. 



This want of accordance between the electrograph and mag- 

 netographs was also well marked daring the August aurora, and 

 woidd appear to prove that the electrical disturbances in the 

 upper aerial strata during aurora do not cause changes of tension 

 in the lower at all commen-urable with those ordinarily produced 

 by wind, snow, or rain. G. M. Whipple 



Kew Observatory, February 2 



The commencement of the aurora consisted in the sudden 

 lighting up of various portions of the sky by patches of white 

 cloud, the northern horizon remaining constantly bright, and 

 sending forth vertical .^treamers. The general appearance of 

 the heavens was that of a smooth lake ruffled here and there 

 every other second by fitful gusts of wind. 



At 6.45 p.m. no ordinary clouds could be seen, but the 

 flashes of white light were incessant, and varied continually in 

 position. The light was strongest towards the north-east 

 horizon, but the whole of the north was well lit up from north- 

 east to west. 



At 6.50 the streamers from the horizon increased in length 

 and enveloped Polaris. 



At 6.55 the number of the streamers increa-ed, and springing 

 from the whole northern horizon, traversed an imperfect arch of 

 white light which passed between e and f Ursse, and just below 

 <J and 7 Ursje Minoris. 



At 6.57 streamers lo° west of north passed from the horizon 

 through the zenith, and the display was becoming very brilliant 

 when I was obliged to enter the ob.iervatory for a few minutes 

 to observe an eclipse of Jupiter's second satellite. 



On returning to the garden at 7h. 5m. nothing remained of 

 the aurora except patches of white light in different parts of the 

 heavens, and a strong glow in the north. Using a hand spectro- 

 scope I could see the green auroral line very strongly marked in 

 every part of the sky, but no other line was visible. 



There was no change in the phenomenon until 7h. 45m., when 

 a most brilliant cone of light of a rcddi.-h hue darted from 

 between a. and 7 Aquarii, and developed almost immediately 

 into a number of streamers which stretched out towards the 

 Pleiades, this cluster being then some 30° from the zenith 

 towards the west of south. Other streamers also appeared near 

 the horizon from the west point to east of north. 



A lull succeeded this display, followed at 6h. 15 n. by a grand 

 outburst of red streamers from Aquarius and al-o from near 

 Orion, both converging towards the Plei.ades, those from 

 Aquarius being the brightest. These were visible for at least six 

 seconds along with other rays in the north-west. 



Cloud and haze were then collecting fast, and seven-tenths of 

 the sky was already obscured. During this aurora the three 

 self-recording magnets were very much disturbed, their move- 

 ments being all rapid and extended. During the whole of the 



morning of the 31st the declination was very irregular, but i 

 was only about noon that the storm began in earnest. From 3.30 

 untd 9 p.m. the declination magnet was oscillating incessantly in 

 long vibrations, several of fully a degree in extent ; and between 

 7h. SS""' ^""^ ^ P-™' 'lis western bearing increased by 1° 37' 24". 

 Many other movements were nearly equally rapid, but not so 

 extensive. The movements of the horizontal force magnet were 

 irregular from noon till after midnight, and they were very much 

 exaggerated between 3h. 45m. p.m. and 8. 15 ; the most rapid 

 change was the remarkable diminution of 2'lm. in the ordinate 

 between 6.14 and 6.20 p.m. ; this was preceded by a very quick 

 rise, and followed by another nearly equally sharp. 



The vertical force magnet was most irregular between 2 p.m. 

 on the 31st and i a.m. on the morning of the l.st. The extreme 

 maximum was attained at 4h. 20m., and the two principal 

 minima at 8h. 12m. p.m., and at 12m. after midnight. The move- 

 ment was most rapid at 8 p.m., and this principal disturbance on 

 all the curves coincided with the grand outbursts of red streamers 

 which converged towards a point some 30° south of the zenith. 



Stonyhnrst Observatory, February S. J. Perry 



Mr. E. Dowlen has been again good enough to furnish me 

 with notes on the aurora (of Monday last), as seen from Med way, 

 Poynton, Cheshire. 



He first saw it at 6. 30, it having been previously seen at 6 as a 

 single shaft of white light. At 6.30 it consisted of quickly-darting 

 rays and waving cnrtains of light, filling almost the whole sky. 

 The horizon from extreme east to west was glowing, and from 

 all this region streamers and waves of light shot upwards, 

 meeting at or near the Pleiades, the rays often passing into Orion. 

 About 7.0 the light in the north-west extending from Venus to 

 some distance north of the moon was rose-coloured ; the other 

 parts were vihite. Now for a few minutes the display almost 

 ceased and clouds began to come up in the north-east ; but the 

 glow increased in brilliancy in the north and north-west, forming 

 a concave mass of light, almost an inverted arch ; and from this 

 sprang a Ijr oad band of streamers filling up all the northern 

 region, and reaching almost to the zenith. This died down, and 

 was succeeded by a similar disj^lay having a drifting movement 

 westward, and a rose tint in the upper portion, which extended 

 throughout it a> it \\ent westward. This display also died out, 

 and was follou el by another similar band more to the west, 

 white in colour. 



At 7.30 this was gone, and the whole aurora gradually grew 

 smaller, the glow still remaining and giving feeble spurts until 

 S.30. About 9.30 the clouds were all gone, and Mr. Dowlen 

 saw that a Ion.; low arch of inconsideiabie width but tolerable 

 brightness had been formed ; the crown of the arch being just 

 above Arided in Cygnu<;. No streamers came from this arch, 

 but there seemed to be a fringe of glow to it. At midnight it 

 faded away. During the whole time there was no wind ; and 

 although there was a ground-frost, the temperature up to 9 o'clock, 

 by thermometer without frame suspended at the end of a bough 

 four feet from the ground, was 34°. At 5 p.m. there had been 

 a sharp shower of rain. Mr. Dowlen had no access to a spec- 

 troscope at the beginning. Later on he saw only the citron line. 



At Guildown the display was not seen, and some fog prevailed. 

 On the Monday morning at 8 a m. a thermometer read 35° in a 

 Stevenson cage four feet from the ground, while ice one-eighth 

 of an inch thick lay on the garden paths. 



The shower of rain is interesting in connection with the sus- 

 picion that the aurora is generally formed in a mist or vapour 

 region. I have seen several eye-descriptions of this aurora, but 

 no spectroscopic ones up to the present date. 



GuildowMi, February 4 J. Rand Capron 



This was a display of aurora borealis having appearances quite 

 new to me. There w-as a faint auroral glare at 6 p.m. ; at 

 6h. iSm. a confused but brilliant mass of light was situated west 

 of Ursa Major, which moved quickly horizontally towards the 

 west, there was also another mass of pink light in Wcst, streamers 

 shot up to the altitude of Cassiopeia. 6h. 24m. the first-mentioned 

 mass of light was now mostly to the west of Cassiopeia. There 

 was also another mass of light low down in north hy east. Stars 

 shone brightly through the aurora, but without scintillation, and 

 somewhat orange-coloured. 6h. 25m. brilliant .streamers in 

 north-east, a wavy arch stretched from west-north-west to east, 

 its east end terminating in a black, almost perpendicular mass. 

 There were also smaller black patches but quite distinct in 

 character to the first-mentioned one. The low dark segment had 

 also a wavy edge, and there was a patch of strong light above 



