534 



NA rURE 



[June 30, 1910 



Halley's Comet. — In Circular No. 3 of the Transvaal 

 Observatory Mr. Innes publishes the observations of the 

 tail of Halley's comet recorded by himself, Mr. H. E. 

 Wood, and Mr. W. M. Worssell during May 17-21. 

 Small sketches showing the form of the multiple tail at 

 various times are also reproduced. In addition to the 

 main tail there were two fainter glows separated by some 

 degrees from the main stream near Pegasus, but re- 

 approaching it in the neighbourhood of Aquila. Quite 

 unexpectedly, as recorded by Mr. Payn and other observers, 

 the remnants of the tails persisted in the eastern sky after 

 the comet had passed the earth, and were seen each morn- 

 ing until the moon interfered, after May 21 ; but it was 

 obvious that they were gradually fading away. On the 

 morning of May 20 the tail was traced to R.A. igh., 

 dec. 5° S., 150° from the invisible nucleus. In a letter 

 to Mr. Innes, Mr. H. C. Reeve, of Lorentzville, states 

 that at 5 a.m. on May 19 the magnificent main tail ex- 

 tended to the Milky Way, and its attendant shafts were 

 respectively 15° and 20° long, giving the whole the appear- 

 ance of a huge transparent cone into which the earth was 

 rushing. On the evening of May 19 the whole comet was 

 south of the ecliptic, yet on the morning of May 20 the 

 original, branched tail was still west of the sun and north 

 of the ecliptic. 



Mr. Finlay and Prof. Rudge, at Bloemfontein, report 

 having seen a rupture of the tail, near Aquila, take place 

 on the morning of May 18-19, but this was not recorded 

 by any other observers. 



Photographs of the comet were taken at the Transvaal 

 Observatory, with the Franklin-Adams star camera, on 

 every possible occasion, and are to be discussed in a sub- 

 sequent Circular ; one of them is reproduced on a plate 

 which accompanies No. 4420 of the Astronomische Nach- 

 richten. The chief characteristic of all the photographs 

 is the complicated structure of the tail. Two groups of 

 streamers are seen on either side of the axis, and, in 

 addition, there are several side streamers showing kinks 

 and irregularities ; the photographs, in many points, 

 resemble many of those taken of Morehouse's comet in 

 1908. 



The Astronomische Nachrichten also contains notes from 

 several Continental observatories generally confirming the 

 results already published. 



In the Comptes rendus for June 20 (No. 25, p. 1659) 

 M. J. Comas Sola gives a restimd of the physical observa- 

 tions of the comet made, visually and photographically, 

 with the 38-cm. refractor of the Fabra Observatory, during 

 the periods of greatest brightness as a morning and as an 

 evening object. 



The comet began to be perceptible to the naked eye, at 

 Fabra, on April 15, and the length of the tail whilst near 

 perihelion was about 50 million kilometres (31-2 million 

 miles). There were distinct changes in all parts of the 

 comet after its inferior conjunction with the sun. 



Before conjunction the tail was generally bifurcated and 

 made up of numerous long filaments, without knots or 

 sharp bends ; M. Sola suggests that this simple straight 

 appearance was the result of the intense repulsive action 

 of the sun while the comet was so near to it. The head 

 was relatively small, although surrounded by very feeble 

 and extensive envelopes ; measurements of the photographs 

 generally give 110,000 km. (nearly 70,000 miles) as the 

 diameter of the brightest part. Generally, the envelopes 

 were eccentrically placed in regard to the axis of the tail, 

 a feature which was very marked on May 11. The nucleus 

 was very bright, and its diameter was about 3500 km. 

 (nearly 2200 miles). 



After conjunction, the tail was not bifurcated ; on May 30 

 it was like a brush of numerous short hairs, and from 

 May 31 it appeared as an aigrette, which became modified 

 from day to day. The bright part of the head was larger, 

 its diameter being about 160,000 km. (100,000 miles), but 

 the fainter envelopes were reduced. The nucleus at this 

 time was very small, probably not more than 1000 km. 

 (621; miles) in diameter. 



Measurements of the photographs of Mav 30 and 31 

 indicate^ that, within two million kilometres of the nucleus, 

 the projected matter travelled at about 23 km. per sec. In 

 a previous note M. Sola referred to projections from the 

 head into the tail, and to the doubling of the nucleus on 



NO. 2122, VOL. 83] 



June 2 ; also to the appearance of several rapidly moving 

 condensations on June 4. He now suggests that these 

 appearances were a series of phosphorescent emanations 

 which seemed to commence about May 31, and coincided 

 with the change in the structure of the tail. Not wishing 

 to state definitely the nature of these ejecta, he calls them 

 globes, and gives some measures of their apparent distances 

 on June 4. Taking a mean, he finds for the velocity with 

 which a globe receded from the nucleus, 527 km. per 

 second. All these globes appeared to vanish at a distance 

 of about 25,000 km. from the nucleus. 



Observations of Winnecke's Comet (igogd). — In No. 

 4420 of the Astronomische Nachrichten Herr R. Prager 

 gives a number of positions of Winnecke's comet observed 

 with the 24-inch refractor of the Santiago de Chile 

 Observatory between November 2 and December 13, 1909. 

 At all times the comet was very faint, appearing as a 

 circular patch of light 0-7' in diameter, and having no tail 

 or nucleus ; after December 13 it was too faint to be seen. 



Colour of Comet 19100 during its Perihelion 

 Passage. — Observed at the Transvaal Observatory on 

 January 17, the great comet 1910a was near the zenith, 

 and therefore practically free from the colour-absorption 

 effects of our atmosphere. Mr. Innes records that, under 

 these conditions, it was identical in colour with, and almost 

 indistinguishable from, the pure snowy-white, alto-cumulus 

 clouds which were passing at the same time (Circular 

 No. 3, p. 21). 



THE INTERNATIONAL BOTANIC CONGRESS 



AT BRUSSELS. 

 T^HERE was a large and representative gathering of 

 botanists in Brussels on the occasion of the Inter- 

 national Botanical Congress on May 14-22. The inaugural 

 meeting took place in the large rotunda at the Botanic 

 Gardens, but the serious work of the congress v.f'as carried 

 out in the Salle des Fetes in the grounds of the Exposition. 

 The important subjects of deliberation were further con- 

 sideration of the rules of systematic nomenclature and a 

 series of propositions on phytogeographical nomenclature. 

 The rules of systematic nomenclature which were drawn 

 up as the result of the deliberations of the Vienna Congress 

 in 1905 left open for future discussion special points in 

 relation to non-vascular cryptogams and palaeobotany. A 

 number of sectional committees were appointed, and their 

 recommendations formed the subject of debate at the 

 recent congress. The chief matter for discussion was the 

 starting points for nomenclature in the various groups. 

 Was the date of publication of Linnaeus 's " Species 

 Plantarum," 1753, which had been adopted as the 

 beginning of nomenclature for seed-plants and ferns, to 

 be the universal starting point throughout the plant 

 kingdom, or would it be preferable to take the date of 

 publication of later systematic works dealing with the 

 various groups of cellular cryptogams? 



After some informal discussion among the workers in 

 the groups in question, a series of recommendations w^as 

 agreed to by the congress. The date 1753 was accepted 

 as the starting point for the Mycetozoa, Algae (excepting 

 certain groups to be noted below), CharaceaJ, Sphagnaceae, 

 HepaticcB, and Lichens. The exceptions to the general 

 rule for the Algse were as follows : — Desmids, J. Ralfs, 

 "British Desmidiese," 1848; Oedogoniaceae, K. E. Hirn, 

 " Monographie u. Iconographie der Oedogoniaceae," 1900; 

 Nostocaceae, M. Gonont, " Nostocac^es homocyst6es," 

 1890, and E. Bornet and Flahault, " Nostocac6es h6tero- 

 cyst^es," 1886-8. 



For the Fungi, Fries " Systema Mycologicum," 1821-32, 

 was adopted as the point of departure, excepting for the 

 Uredineae, Ustilagineae, and Gasteromycetes, which it was 

 agreed should date from Persoon's " Synopsis," 1801. For 

 Mosses, Hedwig's " Species Muscorum," 1801, was agreed 

 upon. In order to reduce to a minimum changes of names 

 which would result in cases where an early date was 

 adopted as a starting point, special committees were 

 appointed for each of the large groups to draw up lists 

 of nomina conservanda, or names of genera which, from 

 long-established use, should be retained, though inadmis- 

 sible on grounds of strict priority. These lists will be put 



