October 4, 1906] 



NA TURE 



575 



OVR ASTRONOMICAL COLUMN. 



Comet igo6e (Kopif). — Circular No. 91 from the Kiol 

 Centralstelle contains a set of elenienls for comet igoGt, 

 calculated by Herr .M. Ebell from positions observed on 

 August 23 and 31 and September 12. 



These elements give the time of perihelion as May 309, 

 1906, and from them Herr Kbell has calculated an 

 epheineris from which the following is taken ;— 



.■\t present the diminishing brightness of the comet is 

 about half what it was on August 23, when its magni- 

 tude was about ii-s. 



From the ephemeris it may be seen that this object is 

 still fn the constellation Pegasus, about half-way between 

 f and 34 Pegasi, and is observable throughout the evening. 



Observing at Rome on September 12, Prof. Millosevich 

 found it to be a faint object having a coma which was 

 not symmetrical about the thirteenth-magnitude nucleus. 



Finlay's Comet, igo6d. — M. Ltopold Schulhof continues 

 his ephemeris for Finlay's comet in No. 4122 of the Astro- 

 nomische Nachrichlen, from whence the following abstract 

 is taken ; — ■ 



Ephemeris 1 

 a(app.) S(app.) 



C.l/.T. Paris). 



1906 a (app.) 



5(app ) 



Oct. 



7 37 

 7 46 

 7 54 



Oct. 16 



+ 20 33 

 + 20 39 



^-20 44 



The comet, according to this ephemeris, i 

 constellation Gemini, travelling directly 

 Cancer, and rises at about 11.30 p.m. 



8 8 

 8 14 



.. + 20 49 

 ... -20 54 

 ... +20 59 

 ow in the 

 stwards towards 

 It will be about 



one degree south of /i Cancri on October 16. 



Two photographs of this comet are reproduced in the 

 September number of the Bulletin de la Sociiii astro- 

 nomique de France. They were taken at the Juvisy 

 Observatory on August 21 and 22 respectively by M. 

 Qu^nisset, and show a well-marked nucleus ; a rudimentary 

 tail is also seen on the original negative. During the 

 exposure on August 21 the comet passed over a tenth- 

 magnitude star, the light of which was not perceptibly 

 diminished by the interposition of the coma. 



-•\ New Form of Wedge Photometer. — In No. 4120 of 

 the Astronomische Nachrichten Herr H. Rosenberg de- 

 scribes, and gives a drawing of, a new form of wedge 

 photometer which he has designed. In the ordinary photo- 

 meter of the " wedge " type the observer is unable to 

 eliminate the influence of the variation in the brightness of 

 the general background of sky, and the eye, becoming 

 fatigued, is unable to determine exactly the point of extinc- 

 tion. 



In Herr Rosenberg's apparatus, however, the image of 

 an artificial star, formed by a constant light source, is 

 projected alongside the image of the natural star, and the 

 wedge adjusted until the two images are equally bright. 

 By adjusting the brightness of the artificial star, so that 

 it is less than that of the faintest object which is to be 

 examined, and determining its value in magnitudes, one 

 may thus measure the brightness of any stars within the 

 limits of about eight magnitudes. The error caused by the 

 the exact point of extinction is thus 



Rosenberg's description states that 



of a similar contrivance was de- 



r in No. 3693 of the Astronomische 



instrument was constructed at the 



uncertamty as 

 eliminated. 



.■\ postscript to Her 

 he finds the principl 

 scribed by Herr Mull 

 Nachrichten, and an 

 Potsdam Observatory. 



OccuLT.ATtoN of .\ St.4r BY Venus. — In a communication 

 to the British .Astronomical Association, published in 

 No. 9, vol. xvi., of the Journal, Dr. Downing directs the 

 attention of amateur astronoTiiers in Australasia to the fact 

 that on December g Venus will occult the third-magnitude 



NO. 1927, VOL. 74] 



star /3 Scorpii. As it is such a rare occurrence for a planet 

 to occult so bright a star, he gives the particulars of the 

 occultation for Sydney, Brisbane, and Wellington in the 

 hope that use may be made of them by observers suitably 

 located. 



Results of the I.nternation.m. L.\titude Service, 1902- 

 1906.— In No. 4121 of the Astronomische Nachrichten Prof. 

 Th. Albrecht discusses the results obtained by the six 

 international latitude stations during the period 1902-0- 

 19060. The variation of the position of the apparent pole 

 is shown on a diagram, which includes the tenths of each 

 year from 19000 to the beginning of the present year. 

 The values given for the period 19020-19050 arc final, but 

 those for igo5' 1-19060 are only provisory, although Prof. 

 .Albrecht states that they are probably correct to one two- 

 hundredth of a second. 



The A.mana Meteorite. — .An interesting description of the 

 various meteoritic objects which fell at Amana, Iowa, 

 U.S.A., in 1875, is given by Dr. G. D. Hinrichs in Das 

 Weltall for September 15. Two plates accompanying the 

 description show photographic reproductions of the 

 meteorites, together with the names of the museums 

 wherein they are now to be found. Other illustrations 

 give charts of the locality in which these objects were 

 discovered. 



BOTANY .AT THE BRITISH ASSOCI.iTION. 

 'T'HE work of Section K was not characterised by the 

 announcement of any discovery of very exceptional 

 interest, nor by any sensational feature. .As has been 

 usual in recent years, an effort was made to group the 

 papers presented so that those dealing with allied topics 

 were taken at the same session. The whole number of 

 papers read was not large, and no less than three morning 

 sessions were devoted to discussion of definite topics, the 

 proceedings being opened in each case by one or more 

 papers giving an account of the present position of the 

 subject to be discussed, or presenting facts and conclusions 

 likely to lead <o debate. These discussions were to some 

 extent organised beforehand ; that is to say, the members 

 most likely to contribute usefully to the discussion of a 

 given topic were informed of the intention to hold the 

 discussion some time before the meeting, and were invited 

 to contribute, abstracts of the opening papers being dis- 

 tributed to them as early as possible, so that they were 

 in possession of the lines to be taken before the meeting. 

 Such of these members as were present and had signified 

 their willingness to speak were called upon in succession 

 by the chairman as soon as the papers were over, the dis- 

 cussion being afterwards open to any member of the 

 section. Although it is true that very good discussions 

 often arise quite spontaneously after papers which are not 

 expected to provoke debate, it is believed that on the 

 whole the best results are obtained by the method of semi- 

 organised discussion described, though it is neither possible 

 nor desirable to limit the sectional meetings entirely to 

 proceedings of this type. 



The success of such discussions depends very largely on 

 the selection of topics of suitable scope. On the whole 

 the tendency is to take too wide a subject, with the result 

 that the different speakers are apt to deal with quite 

 distinct aspects of it, and unless the opener has the ex- 

 ceptional power of drawing all the threads together in his 

 reply the impression left on hearers is liable to be some- 

 what inconclusive and chaotic. On the other hand, if the 

 subject chosen is too narrow, its treatment is apt to be- 

 come excessively technical, the discussion is of limited 

 interest, and may even languish owing to a lack of 

 sufficiently instructed specialists. 



Of the three discussions at the York meeting, the first 

 was taken on Friday morning, August 3, and was really 

 divided into two parts. Dr. D. H. Scott opened the 

 session. Though his title was a wide one — " Some .Aspects 

 of the Present" Position of Palreozoic Botany " — consider- 

 ations of time compelled Dr. Scott to limit himself to 

 " the diflRcult question of the position of the ferns in the 

 Pal.Tsozoic flora," " the difficulty arising from the accumu- 

 lation of evidence showing that most of the so-called 



