Oct. 12, 1882] 



NATURE 



57i 



found in such treatises, we find Jamin's researches on 

 laminated magnets, the thermoelectric effect discovered 

 by Bouty between a metal and its salt, the so-called in- 

 ternal-current galvanometer of Conrad Cooke, and other 

 matters. Many of the drawings are new and suggestive, 

 though some of them (for example, the Ruhmkorff's coil 

 on p. 189) are not quite on the level of the usual excel- 

 lence of French scientific illustrations. We have serious 

 fault to find only with one minor point ; M. Gariel gives 

 - in detail the researches of Wheatstone, Fizeau, and 

 Guillemin on the (supposed) "velocity of electricity," 

 without letting his readers know that the apparent velocity 

 of an electric wave which these observers essayed to de- 

 termine, is a very different thing from the velocity of 

 electricity itself, to which no man can assign any definite 

 value whatever, and which may be infinite or infinitesimal. 

 We congratulate M. Gariel and wish his work success. 



LETTERS TO THE EDITOR 

 [The Editor dots not hold himstlj responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 Ao no/ice is taken of anonymous communications. 

 [The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to ensure the appearance even 

 of communications containing interesting; and novel facts.] 

 The Recent Magnetic Storm and Aurora 

 • The following particulars of the magnetic storm of October 

 2, and of the aurora which accompanied it, may be of interest 



At 2lh. 40m. G.M.T. on October I, a sudden disturbance of 

 the magnetic decimation and horizontal force commenced, and 

 the motions were rapid, though not exceptionally large, until 

 about oh. 50m. on October 2, when a large decrease of declina- 

 tion and horizontal force took place. From about 6h. 50m to 

 7h. 20m. the declination diminished 1°, and the horizontal force 

 about 1.70th part. The motions were active till nh., less so 

 till 14b. or 15b., when the disturbance ended. There was much 

 activity betw een o.h. and loh. 



Both earth-current traces showed a sudden commencement of 

 disturbance at 2ih. 40m., just as in the case of the magnetic 

 registers the time; of greatest activity, and the time of cessation 

 ot disturbance being also coincident. As is usually the case 

 earth-currents were more active along the north and south line' 

 than along the east and west. 



As regards the aurora, a bright arch extended along the north 

 horizon to an altitude of 20° from 6h. 48m. to 7 4h., and remark- 

 able outbursts of streamers were noted from 63 h . to 7lh and 

 from 9 h Sm. to 9 h. 25m., corresponding closely in point of 

 time with the more active parts of the magnetic disturbance. 

 Patches of phosphorescent light were seen in various parts of the 

 southern sky between yh. and 7I1. 36m., and ruddy light (prin- 

 cipally near Arcturus) was observed between 6|h and 7ih 



In connection with this magnetic disturbance it is 'to be 

 remarked that a large spot was on the central meridian of the 

 sun on September 30, having been first seen near the east limb 

 on September 25. It increased considerably in size as it passed 

 across the disc, and its dimensions on September 30 were — 

 ength, 108 ; breadth, 65"; area of whole spot (in millionths of 

 the suns visible hemisphere), 990; of umbra, 215. There was 

 a line of smaller spots following it 128" in length, with an area 

 of 520, and a spot of considerable size near the equator, forming 



Z?frt eT V V ! th lh£ ' ar8e S P 0t > three S P° ,S ™ ibi * to the 

 naked e>e. The large spot was nearly in the same position on 



L'hIT f."' 6 !?' s P ot of last A P ri >- to heliographic 

 ongitude being 5,°, and latitude 22° S., whilst the position of 

 the great spot on April 10 was long. 65°, lat. 29° S., and at its 

 next return long. 52°, lat. 29' S. \v. H. M. Christie 



Koyal Observatory, Greenwich, October 9 



An aurora of unusual form appeared here this evening at 7 8 

 p.m My attention was attracted by a patch of light in the 

 ■Burn-west about 10 above the horizon, and about t° in dia- 



meter. On looking to the north, I saw the usual streamers and 

 bright light indicating an aurora ; presently another patch of 

 light, similar to the first, appeared in the south-east, and then 

 others between these two, forming a continuous arch lying as 

 near as I could julge, in the diurnal path of the sun 'in mid- 

 winter. The arch had a sharp outline below, and from the 

 brightest portion of it extended short streamers, towards the 

 zenith ; the colour was a greenish white. In a few minutes t'-e 

 continuous arch disappeared, leaving the brightest portions, 

 which disappeared and reappeared alternately in patches until 

 7.40, when the last rather suddenly died out. 



The light in the north was not particularly bright, nor were 

 the streamers so continuous or numerous as usual, but that in the 

 south showed up most brilliantly against the black sky near the 

 horizon, so much so that the appearance was as if a dark cloud 

 of circular outline was coming up from the south, and cutting off 

 the lower portions of the auroral light. Geo. M. Seabroke 



Temple Observatory, Rugby, October 2 



The aurora of Monday, the 2nd infant, was succeeded by 

 another on the following night at 11 p.m. It a-sumed the form 

 of pale streamers issuing from a point in the horizon about north 

 by east, and uniting in a similar way directlv opposite in the 

 south, like the meridian lines marked on a globe. The streamer 

 crossing the zenith was the brightest. A. Percy Smith 



Temple Observatory, Rugby, October 6 



The communication below is from a lady. I was on the 

 road from Hilton to this town (and several miles distant from 

 the residence of my correspondent), when I observed the o-reat 

 di-play she alludes to. I also saw the white clouds or nodes 

 and at the moment I thought it itas a lunar rainbow, similar to 

 one I described in vol. xx. of British As-ociation Reports (1850) 

 but upon considering that the moon had not then risen, and 

 turning round 1 saw the grand appearance. 



St. Ives, Hunts., October 6. J. King Watts 



A most splendid and beautiful aurora borealis was visible for 

 a long time yesterday evening, October 2 in this town, com- 

 mencing at 6h. 40m. The wearher had been precarious all day 

 In the early morning there Mas a thick white fog, the wind 

 being south-west. The wind afterwards changed from that point 

 to the north-east, then in the afternoon to the north The sky 

 had been much overcast, and some slight showers of rain fell at 

 intervals. The wind then suddenly changed to the west for a 

 short time and then back to the norlh, gently driving the'clouds 

 away to the south-east. The aurora then became visible and 

 was most gorgeous and brilliant, throwing up incessantly various 

 coloured streamers, and many flashes of white light which 

 passed several degrees beyond the zenith. When the moon arose 

 shortly after 9 p.m. the appearance was still in existence and 

 was very singular and impressive. During the display and until 

 the aurora had finally disappeared, two large white clouds or 

 nodes were visible, one being similar to a large lump, and the 

 other streaming, and of great brilliancy, in the opposite direction 

 and they continued so for some time after the aurora had finally 

 disappeared Anne Gifford 



Over Cambs., October 3 



I see in Nature (p. 548) notices of an unusual aurora that 

 was seen on the evening of October 2. The following observa- 

 tion may be of interest. At 5.30 p.m. that evening, while it 

 was still quite light, I noticed a band of "mare's tail" cirrus 

 extending from the horizon about north-east, through the zenith 

 to the horizon about south-west ; the texture of the cloud— which 

 I may mention somewhat resembled the backbone of a fish— 

 indicated that it was one of the highest sorts of cirrus The 

 sky at that time was unusually clear of other cirri ; and this rib 

 attracted my attention by its unusual length in isolation. Perhaps 

 further observations may tend to show that these high clouds 

 owe something of their arrangement to electrical causes 



Cheltenham, October 6 \y. I.ari.en 



It may be worth mentioning that the aurora on the evening 

 of the 2nd inst. was observed at sea on board the Guion s s 

 Arizona in about Lat. 51° N. and Long. 2S° W., or about 700 

 miles west of Cape Clear. I first noticed it soon after 7 p m 

 J -hips time), but the most brilliant display which I saw was 

 between 12 and 12.15 P-m. (G.M.T. ), when sheets of light 



