350 



NATURE 



[January 12, 191 1 



in which a number of rays appear to emanate from a 

 point immediately behind the nucleus, while the envelopes 

 around the nucleus appear to form a cap over the tail. 

 Extraordinary irregularities and contortions are shown on 

 the photograph of May 21, which is an exceptional one. 

 The first photograph of the series, taken on April 11, 

 showed a fan-shaped tail 9' long after 4 minutes' expo- 

 sure. This gradually increased, and on April 19 (37 

 minutes) a tail of 7° 45' long was depicted, which was 

 straight for 4° and then appeared to be blown to the 

 south quite suddenly, the remaining part being very faint. 

 A very confused, intricate, and contorted tail was photo- 

 graphed on April 21, one bright streamer, forming the 

 northern boundary, bending twice at right angles at about 

 4S' from the head. 



On May 4 the photograph which we here reproduce, 



from one of the 

 direct prints, was 

 taken with 30 

 minutes' expo- 

 sure, and shows 

 a tail 15° long to 

 the edge of the 

 plate. At 5° from 

 the head the 

 breadth was 1°, 

 and the tail 

 appears to be 

 composed of a 

 large number . of. 

 overlying shafts 

 with a central 

 bright streak. 



The southern 



edge is slightly 

 convex, an d 

 shows a number 

 of delicate 

 branches emerg- 

 ing from it with 

 striking regu- 

 larity; the 

 northern edge is 

 quite simple. 



Later photo- 

 graphs show a 

 great number of 

 streamers, ten 

 rays being visible 

 near the head on 

 May 8; but the 

 tail was straight, 

 no branching of 

 the streamers 

 being shown. 

 Three days later 

 the tail was 

 bifurcated by a 

 dark central 

 space, along the 

 north edge of 

 which there was 

 a bright ray ; this 

 division was 

 accentuated on a 

 later photograph 

 taken on May 11. An elongation of the head appeared 

 on May 12, when the envelopes about the nucleus 

 extended to a distance of 1° behind it. The last photo- 

 graph before transit was taken on May 16 with 12 minutes' 

 exposure, and shows 9° of tail, which was 2° 5' wide at a 

 distance of 5° from the nucleus. The greater brightness 

 of the envelopes on the southern edge is noticeable to a 

 distance of 1° from the nucleus, and the tail appears quite 

 simple, without rifts or rays. 



After the transit, on May 21, a condensed stellar nucleus 

 was shown on the photographs, and the envelopes on the 

 northern edge were stronger than those on the southern. 

 But on May 25 the envelopes were apparently symmetrical, 

 and two days later the nucleus was very bright, and there 

 was no visible condensation. On June 25 the head was 

 much broader than the tail, and appeared to be granular, 



NO. 2150, VOL. 85] 



FjG. I. — Halley's Comet, May 4, 1910. Photo- 

 graphed at ttie Transvaal Observatory. Ex- 

 posure 30 minutes. 



suggesting a very close cluster of small stars; this, Mr 

 Wood suggests, may be a photographic effect. Althou};; 

 on several photographs taken in June the head is describui 

 as being large, no mention is made here of the division 

 of the nucleus as recorded by other observers. 



The circular also contains a most interesting reswn< 

 of the measured lengths of the tail recorded visually \,\ 

 Messrs. Innes and Worssell. The greatest apparent lengti 

 was on May 19, when the tail extended 150° from tli 

 assumed position of the head; the greatest length actuall. 

 seen and measured, with the whole comet visible, w:i 

 107°, on May 17. As mentioned in an earlier circular, 

 the eastern, or morning, tails were seen at Johannesburg 

 three days after the transit of the comet, but Mr. Inm > 

 believes that a rupture took place before May 18, and 

 that the eastern tails seen on May 21 were not then con- 

 nected with the main body of the comet. Mr. Innes 's 

 testimony as to the magnificence of the comet is worth 

 quoting here. He says : — " It may be said that it would 

 require much imagination to desire a more impressive an ' 

 brilliant spectacle than that presented by Halley's comi 

 on the mornings of May 15, 16, and 17. It was inde' i 

 a ' Great Comet,' such as the writer had never seen befor 

 and can hardly expect to see again." 



No less interesting are the notes regarding the gener; ' 

 visual appearances between January 25 and July 6, bu: 

 space will not permit mention of more than a few of 

 them. A secondary nucleus was measured on April 16, 

 and was then 12", in position angle 48-3°, from th 

 primary ; this appearance of a second nucleus was nn. 

 persistent, but was recorded, on and off, many times. 

 The drawings from the visual observations are reproduced 

 on. Plates x. and xi., and form a valuable record of the 

 innumerable changes in the various phenomena attending 

 the comet during the apparition. On May 6 the head 

 was decidedly yellowish, an appearance not noted before, 

 and the tail apparently intercepted about half the light 

 of the star B.D. -f8-5°, reducing its relative magnitude 

 by 0-8. The nucleus and bright coma were also recorded 

 as decidedly yellow on May 12, when, the jets from the 

 nucleus had a most extraordinarily complicated appear 

 ance, which was accentuated on the succeeding day (s( 

 Nos. 31-34, Fig. 2). • • 



. After the transit the visual observations showed a stelln: 

 nucleus without jets or rays, which, however, developed 

 later. The nucleus, too, changed and became multiple,-, 

 and three nuclei were recorded on June 2. Later, the 

 separate- nuclei . appear to. have become diffuse, and on 

 June 4 had the appearance of a large, out-of-focus double 

 star,- distance about 4", almost resolved ; the colour was- 

 still yellow. By July 6 the head, although much brighter 

 in the centre, showed no stellar nucleus. - 



Father Goetz, of the Buluwayo Observatory, also con- 

 tributes some I notes of visual observations, and gives a 

 sketch of the comet's head as seen on May 13 ; a peculiar 

 feature is a much brighter segment of the inner envelopes 

 immediately in front of the nucleus. Two faint stars wer< 

 seen through the coma on May 21, and were not appreci 

 ably dimmed. 



A number of meteorological phenomena were recorded 

 by the observatory staff and by numerous correspondents. 

 Especially interesting are the lunar-halo phenomen.a 

 depicted on Plate xii., and the note that unusually high 

 temperatures were recorded at the observatory during th^ 

 time of the comet's passage. 



Mr. Innes offers to lend, under suitable conditions, th- 

 original drawings reproduced on Plates x. and xi. to an\ 

 recognised investigator who may require them. 



The Utrecht observations of the comet are recorded b- 

 Profs. Niiland and van der Bilt in No. 44.^3 of th- 

 Astronomische NachricMen. They give positions fron 

 December 3, 1909, to May 27, and a number of not' 

 describing the various peculiar phenomena observed. The\ 

 also record the yellow and orange-yellow colour observed 

 early in May, and direct attention to the various shapes 

 and position angles assumed by the head. The sketches 

 made between April 29 and May 6 so nearly resemble, 

 in their peculiar forms, those made by Bessell and 

 others in 1835, that the present observers suggest 

 that the great periodic comet has its own specml 

 phvsiognomv. 



The same iournal contains a record of the observation- 



