February io, 1910] 



NA TURE 



441 



was quite a conspicuous object after the head had set, 

 until it was lost in the moonlight. As the drawing shows, 

 there was, in 'addition to the two main branches of the tail, 

 separated by a dark segment, a fluffy extension on the 

 eastern side ; all these features are shown on the photo- 

 graphs taken the same evening, and mentioned in Nature 

 last week. 



Further observations were made on January 29, and, 

 although the sky was less clear, the length of the tail 

 was estimated by Father Sidgreaves to be 17° or 18° ; the 

 general brilliancy of the comet was less. 



Father Cortie also records some observations made by 

 the Rev. J. Rowland at St. Asaph, N. Wales, who directs 

 attention to " a faint general illumination of the sky to 

 the east of the tail, of a width apparently of 10° to 15°, 

 the length of the tail being over 20°. There was also an 

 apparent deviation of the tail to the east between a. and 

 7 Pegasi." This confirms the independent observations, 

 made at Stonyhurst and elsewhere, as to the apparent 

 existence of a cloud of particles following the eastern 

 branch of the comet's tail. 



Mr. Theodore Kensington, West Malvern, also mentions 

 a similar phenomenon. He says, in a letter dated 

 February 5 : — " The comet was a magnificent sight from 

 the Malvern Hills a week ago, and of even more than 

 ordinary interest owing to the glare which was visible, in 

 apparent connection with it, on its southern side. Tb's 

 glare was best seen on the evenings of January 20 and 30, 

 but it was also visible last Wednesdav and Fridav." 



Mr. Kensington further states that the glow was like 

 that from a distant city or an aurora, but that it was not 

 terrestrial was shown by its setting with the stars. It was 

 like an inverted U the right side, bounded by the comet 

 and the square of Pegasus, reaching nearly to Saturn, 

 while the left (south) side descended almost perpendicularly, 

 but with a slight trend inwards, to the visible horizon. 

 The distinction between the bright background on the one 

 side of the comet and the dark sky on the other side was 

 quite marked, but after January 29 there was a darker 

 band of sky between the comet's tail and this glow. 



Miss Eleonora Armitage, writing from Dadnor, Hereford- 

 shire, states that the glare seen in the neighbourhood of 

 the comet was the zodiacal light, which showed particu- 

 larly well on January 29. She adds : — " The tail of the 

 comet was well defined on the west side, reaching a little 

 beyond and above a Pegasi, as seeii whh the naked eye ; 

 on the east side it could be traced almost so far as 

 7 Pegasi, but along most of this side the edge was very 

 indefinite, owing to the light practically blending with 

 that of the zodiacal liglit, both having apparently the same 

 degree of luminosity. 3 -Aquarii could be seen through 

 the tail a little above the nucleus of the comef. The next 

 cs-ening, January 30, the comet was much fainter, but the 

 tail could still be traced for nearly 30°, while the zodiacal 

 light stretched up in a bright cone, the apex almost reach- 

 NO. 2102, VOL. 82] 



ing to Saturn. When seen again on February 4 the 

 northern movement of the comet had removed it irom. 

 the track of the zodiacal light, so that the two lights 

 appeared to be separated by a segment of dark sky, the 

 eastern edge of the curved tail being now nearly as clearly 

 defined as the western." 



Reports from other observers indicate that the 

 zodiacal light has been well seen on several occasions 

 during the past fortnight. Dr. F. J. .Allen saw it and the 

 comet, under ideal conditions, from the Mendip Hills on 

 January 30, and suggests that the " glare " near the comet 

 as seen by other observers was doubtless the light. A 

 correspondent (" E. W. P.") at Ross, Herefordshire, also, 

 states that " the zodiacal light was distinctly seen this 

 evening at 6.45 (February 4), whilst the tail of the ' day- 

 light .' comet seemed to reach further than ever." 



Dr. Allen's observations of the comet are of especial 

 interest, for he remembers distinctly the comet of 185S 

 (Donati's), and has seen all the bright comets since, and 

 states that, as he saw it on January 30, 1910a is the only 

 one which can be compared in effect with Donati's. The 

 intermediate ones, though brighter than the present one, 

 were poor little things in apparent size. He suggests that 

 the estimates of its apparent size have erred on the side 

 of cautiousness. As he saw it at Cambridge, during the 

 early days of its appearance, his estimates agreed with the 

 usual ones ; but as seen from the Mendips, smoke, gas- 

 lamps, and clouds being absent, and the night exceptionally 

 clear, the tail reached beyond and included o Pegasi, and 

 then took a more pronounced curve to the left. He 

 estimates its length as 40°, and suggests that, had the 

 zodiacal light been absent, the tail might have been traced 

 further, for the light rendered its S.E. limit indefinable; 

 his observations extended for more than an hour, between 

 6 p.m. and 7.30 p.m. Prof. R. A. Gregory, observing at 

 Chichester on January 29 and 30, found that the tail was 

 certainly 30° long, whilst M. Giacobini reports (Comptes 

 rendus. vol. cl.. No. 5, p. 263) that, as seen by the 

 naked eye at the Paris Observatory, on January 29, its 

 length exceeded 45°. M. Chofardet, at Besancon, states 

 that on January 27 the tail was 25° long, and, curving 

 towards the south, mixed its light with that of the 

 zodiacal light. 



In a further communication, Mdlle. de Robeck, observ- 

 ing at Inistioge, Kilkenny, states that on January 29 the 

 comet appeared very much in the same way as shown in 

 Mr. Rolston's sketch in last week's Nature, but the tail 

 seemed to reach higher, and swept upward nearer to 

 a Pegasi. After Venus had set, the tail of the comet was 

 seen like a great search-light sweeping the sky, and the 

 fainter stars below Pegasus were seen glittering brightly 

 through it ; the night was exceptionally clear at Inistioge. 

 Aldlle. de Robeck also states that, before the comet became 

 such a noticeable object, the country people around 

 Inistioge took Venus to be the much-talked-of oljject, and 

 saw in it a portent of dreadful calamities. That the Earl 

 of Crawford's suggestion (Nature, January 20, p. 349) 

 was an urgent one is proved by the reports of " comet 

 scares " in Russia, Turkey, and other countries, occasioned 

 by the sudden and unexpected appearance of igion. It 

 certainly would be well to prepare the native minds foi- 

 the apparition of Halley's comet when, as Mr. Cowelf 

 thinks it will, it becomes sufliciently bright and large to 

 attract general attention. 



Mr. Keeling, of the Helwan Observatory, Egypt, reports 

 that the comet (1910a) was observed on several evenings 

 at Helwan, Egypt, and photographs of it were obtained on 

 January 24, 25, 27, and 28; the camera employed has a 

 Cooke lens of 4 inches aperture and 28 inches focal length. 

 Naked-eye observations on January 27 and 28 showed the 

 tail to be 24° to 25° in length. 



A telegram from Dr. Aitken (Astronomische Nachrichlen, 

 No. 4386, p. 292) states that Dr. Albrecht finds the sodium 

 lines in the spectrum of the comet to be so displaced as 

 to indicate a recession of 66 km. per sec. in the line of 

 sight. As the position of these lines has now. apparently, 

 been measured with sufficient accuracy to justify a definite 

 statement as to " shift," it seems very improbable that the 

 yellow lines observed are due to helium, unless two sets 

 of such lines have been observed, and there is no sugges- 

 tion of this. In this regard Mr. Hinks writes to us dis- 



