448 



NATURE 



\_Sept. 5, 1889 



OUR ASTRONOMICAL COLUMN. 



Yale College Observatory. — The report of this Observa- 

 tory for the year ending June 1889 has recently appeared. Mr. 

 Brown, the Secretary, records the carrying out of several im- 

 provements in the grounds of the Observatory, and the continua- 

 tion of the work of the Thermometric Bureau, 7475 thermometers 

 having been received for verification during the year. Dr. 

 Elkin, the astronomer in charge of the heliometer, completed 

 the measures for the triangulation of the region near the North 

 Pole during the summer of 1888, and the necessary reductions 

 are well advanced. In October 1888 a series of observations for 

 the parallax of Iris was commenced in connection with similar 

 series to be effected at the Cape and at Leipzig, but measures 

 were only obtained on thirty-four instead of sixty-five nights. In 

 addition to these, however, 168 sets, each consisting of sixteen 

 pointings, were obtained by Messrs. Elkin and Hall, for the 

 diurnal parallax of the same planet. The discussion of the whole 

 series of measures has been undertaken by the Yale astronomers, 

 and the work has already been commenced. A series of measures 

 for the parallaxes of Victoria and Sappho are now being under- 

 taken, and it is expected that two additional observatories, those 

 of Bamberg and Gottino;en, will co-operate in the work. The 

 heliometer has also been employed in further researches on stellar 

 parallax ; Procyon and Altair having been taken up by Mr. Hall, 

 Vega and Regulus by Dr. Elkin. During the winter Mr. Hall 

 completed the reductions of his work on the oi-bit of Titan ; 

 whilst Dr. Elkin took part in the observation of the total solar 

 eclipse of January i, 1889, which he observed from Winnemucca, 

 Nevada, under very favourable circumstances. 



New Minor Planet. — A new minor planet, No. 287, was 

 discovered by Prof. Peters at the Clinton Observatory, on 

 August 25. 



Should the two planets discovered on August 3 both be con- 

 firmed as new bodies, that discovered by M. Charlois will be 

 No. 285, whilst Herr Palisa's will be No. 286 ; the former 

 having been discovered at loh. 46m. G. M.T., and the latter 

 at iih. 27m. 



Comet 1889 r/ (Brooks, July 6.)— Dr. K. Zelbr has found 

 elliptic elements for this comet, with a period of 12J years. The 

 ephemeiis from these elements compares as follows with Herr 

 Knopf's ephemeris which is given below : — 



Zelbr- Knopf. 

 1889. R.A. Decl. 



Sept. 8 

 Oct. 2 



-2 17 + 17 



-5 49 +5'i 



Herr Knopf's Ephevieris for Berlin Midnight. 



R.A. 



Did. 



Log r. 



Log A. Bright- 



Sept. 



•• 0-1333 ••• 1-34 



•• 0-I353 ... 1-31 

 .. 0-13^6 ... 1-28 

 .. 0-1430 ... 1-25 



.. 03814 ... 0-1487 ... I-2I 



.. 0-3843 ... 0-1554 ... i-i6 

 .. 0-3873 ... 0-1632 ... I 09 



0-3709 

 0-3734 

 0-3759 

 0-3786 



5 43-8 S 



5 39-0 



5 34 -o 



5 28-6 



5 22-4 



5 15-3 

 Oct. 2 ... 23 56 26 ... 5 7-0 S 

 The brightness on July 8 is taken as unity. ♦ 



Comets 1888 e (Barnard, September 2) and 1889 b 

 (Barnard, March 31). — The following ephemerides are in 

 continuation of those given in Nature for 1889 August i : — 



Sept. 



Oct. 



Reduction of Rutherfurd's Photographs Of the 

 Pleiades and Pr^sepe. — Two papers by Dr. B. A. Gould 

 have recently been published in the memoirs of the National 

 Academy of Sciences, which possess a very special interest at the 

 present time, for they show that in the very dawn of astro- 

 nomical photography, it was possible to determine the relative 

 places of the members of a star-cluster from a series of photo- 



graphs with a precision comparable to that attained even with 

 a heliometer. In 1865, Rutherfurd had obtained a number of 

 photographs of the Pleiades, and early in 1866 he placed the 

 results of his measurements of these plates in the hands of Dr. 

 B. A. Gould, who deduced from them the R.A.'s and Decls. of 

 nearly fifty stars of the group, and who, further, compared these 

 results with the heliometer measures of Bessel, made more than 

 a quarter of a century earlier. The comparison, even as it stood, 

 was a most satisfactory one, for, in spite of imperfections in the 

 method of measuring the photographs, such as naturally occurred 

 in a first essay, the probable error of a measure, either of dis- 

 tance or position, appeared as small for the photograph as for 

 the heliometer, and the general agreement of the two methods was 

 most gratifying. The paper in which this discussion was given, 

 though presented to the Academy on August il, i865, has only 

 recently appeared — a regrettable delay, for it might well have 

 been that so striking a demonstration of the possibilities of the 

 photographic method might have insured its adoption by astro- 

 nomers a decade, or even two, earlier than has actually been the 

 case. Dr. Elkin has now {Astron. Joitr. No. 197) compared 

 Dr. Gould's places of the Pleiades with values interpolated be- 

 tween the Konigsberg heliometer places for 1840, and the Yale 

 places for 1885, and after clearing the photographic results for 

 some systematic errors thus disclosed, he finds the residuals very 

 small indeed. Of sixty-eight values, only one exceeds o"-38, 

 and foity-seven are less than o"-20, nor do they show any system- 

 atic character depending on distance or direction from the centre 

 of the field. The probable error of a co-ordinate from the 

 photographic measurements, he deduces as : — 



For the brighter stars, ± o"-o79, 

 ,, fainter ,, ± o"-ioi. 



Dr. Elkin concludes, therefore, that " the smallness of these 

 probable errors must be convincing proof that in photography we 

 have really a means of investigation for micrometric work at 

 least on a par with any existing methods as regards magni- 

 tude, and doubtless far surpassing them in ease of measurement 

 and output of work." 



The paper on Rutherfurd's photographs of the PrDssepe was 

 presented to the Academy on April 14, 1870, and the central 

 star to which the others were referred being a small one, instead, 

 as in the Pleiades, of a very bright one, which had been, there- 

 fore, always much over-exposed, the results were even more 

 satisfactory. 



ASTRONOMICAL PHENOMENA FOR THE 

 WEEK 1889 SEPTEMBER 8-m. 



/'lIj'OR the reckoning of time the civil day, commencing at 

 ^ Greenwich mean midnight, counting the hours on to 24, 



ij here employed.) 



At Greenwich on September 8 

 San rises, 5h. 26m. ; souths, iih. 57m. 27 9*. ; daily decrease 



of southing, 20-63. ; sets, i8n. 29in. : right asc. on meridian, 



iih. 8-411, ; decl. 5' 32' N. Sidereal Time at Sunset, 



1711. 41m. 

 Moon (Full on September 9, i3h.) rises, i8h. 37m. ; souths, 



23h- 35m. ; sets, 4*1. 4411.* : right as:, on meridian, 



22h. 47 -7m. ; decl, 12^ 20' S. 



Right asc. and declination 

 Planet. Rises. Souths. Sets. on meridian. 



h. ni. h. m. h. m. h. m. o / 



Mercury,. 7 43 — 13 22 ... 19 i ... 12 33-5 ... 4 47 S. 

 Venus ... I 49 .. 9 30 ... 17 II .,, 8 40-3 .. 18 5 N. 

 Mars ... 2 56 .. 10 23 ... 17 50 ... 9 33-7 ... 15 45 N. 

 Jupiter ... 14 50 ... 18 43 .,. 22 36 ... 17 54-6 ... 23 27 S. 

 Saturn ... 3 32 ... 10 47 ... 18 2 ... 9 574 ■•. I3 44 N. 

 Uranus... 8 38 ... 14 4 ... 19 30 ... 13 15-3 ... 7 20 S. 

 Neptune.. 21 12*.. 5 2 ... 12 52 ... 4 11-7 ... 19 26 N. 



* Indicates that the rising is that of the preceding evening and the setting 

 that of the following morning. 

 Sept, h. 



10 ... 19 ... Mercury at greatest distance from the Sun, 



Meteor- Showers , 

 R.A. Decl. 



Near | Persei 

 ,, Aldebaran 

 M Vega ... 



60 



72 



282 



354 



37 N. 

 14 N. 

 42 N. 



38 N. 



Swift ; streaks. 



Swift ; bright. 

 Very swift. 



