112 



NA TURE 



[May 29, 1890 



spectrum of Group II. AH the bands 1-9 are plainly visible ; 

 they are wide and dark throughout the whole length of the 

 spectrum. The chief observations required of such a star as 

 this are direct comparisons with the bright carbon flutings, as 

 their existence in stars of the 2nd group is still not generally 

 accepted, although Dr. Copeland demonstrated it most con- 

 clusively in the so-called "Nova" Orionis. Our ideas of the 

 constitution of this class of stars must turn almost entirely on 

 this point ; if the bright flutings exist, the stars, like comets, 

 must consist of discrete masses. 



(3) This is a star of the solar type (Vogel). The usual 

 observations are required. 



(4) The spectrum of this star is one of Group IV. The usual 

 additional observations are required. 



(5) This highly interesting variable will reach a maximum on 

 May 30. The magnitude at maximum varies from 4 to 6'5, 

 whilst that at minimum is below 13. The change of luminosity 

 is therefore enormous, and it is obvious that many of the ex- 

 planations offered for different kinds of variables, such as 

 variation of spotted area, are quite insufficient for a case like 

 this. The period is about 406 days, but it appears to be shorten- 

 ing. The spectrum is a magnificent one of Group II., and near 

 the maximum last year Mr. Espin noted the presence of bright 

 lines, amongst which the line D3 was very bright. In future 

 observations, the bright carbon flutings should also be carefully 

 examined, as it seems very probable that, if they exist, they will 

 brighten along with the lines of hydrogen and D3. If the 

 principal fluting, near b, be sufficiently bright, the 2nd maximum 

 of the fluting may be bright enough to be measured. The 

 collision theory of variability seems to explain this class of 

 variable in every detail, even to the lengthening of the period, 

 for the retardation which the secondary swarm would undergo 

 at maximum must inevitably in time lengthen the period. 



The Spectrum of Comet Brooks {a 1890).— On the 

 evenings of May 21, 22, and 23, I made some observations of 

 this comet which may not be without interest. On the 21st the 

 appearance of the comet was not unlike that of the Nebula in 

 Andromeda, except that it was almost circular instead of 

 elliptical in shape. The colour of the comet was whitish, and 

 the nucleus was rather ill-defined. The spectrum was to a large 

 extent continuous, but there were also unmistakable bright 

 flutings. These were brightest in the nucleus, but they also 

 extended faintly throughout the whole mass. Direct comparisons 

 with the blue base of a spirit-lamp flame showed coincidences 

 with all the flutings, except the bright one in the violet which is 

 characteristic of hydrocarbons. The fluting near b was by far the 

 brightest, and next in order of intensities came those near A 474 

 and 564. The continuous spectrum extended from about D to 

 a little beyond \ 474. On the 22nd the nucleus was much less 

 central than on the previous evening, probably owing to further 

 development of a short bushy tail. The spectrum, however, 

 showed no obvious differences, except that the brightest fluting 

 had slightly increased in intensity. On the 23rd the form and 

 spectrum were practically the same as on the 22nd. The ob- 

 servations were made with a lo-inch refractor, but the comet 

 was easily seen in the 3-inch finder. 



The comet had obviously got beyond the earlier temperature 

 stages before I observed it, and it will be highly interesting to 

 notice if the further changes indicated by Prof. Lockyer's dis- 

 cussion of cometary spectra (see p. 20) take place. These will 

 be most obvious in the faintest band (\ 564) owing to the super- 

 position of the bright flutings of manganese and lead. Changes 

 of the form or wave-length of this band should therefore be 

 particularly noted in further observations. It is, of course, 

 desirable that the observations should be made independently 

 by more than one observer. In my observations of May 21 I 

 was very much struck by the resemblance of the comet to the 

 Nebula in Andromeda, both in form and colour, and in 

 spectrum. 



On the 27th I again observed the comet, but saw no decided 

 differences, either in its appearance or spectrum. 



A. Fowler. 



New Variable Star in Cygnus.— Prof. Pickering, of 

 Harvard College, notes in Astronomische Nachrichten, No. 2968, 

 that a study of the spectra of the fainter stars is now in progress 

 with the 8-inch Draper telescope. An examination by Mrs. 

 Fleming of photographs taken with small dispersion led to the 

 discovery that the star D.M. -f 48° -2940 whose approximate 

 place for 1900 is in R.A. I9h. 40m. 8s., Decl. -f 48° 32' gave a 



NO. 1074, VOL. 42] 



spectrum resembling that of Mira Ceti and other variables of 

 long period. A photographic chart was made, and on com- 

 parison with the photographs previously taken of this region 

 proved conclusively that the star is a variable. The photographs 

 compared are of three kinds : (i) trails in which the telescope 

 was at rest and the brighter stars formed lines by their diurnal 

 motion ; (2) charts in which the stars formed circular images ; 

 (3) spectra formed by placing a prism in front of the object- 

 glass. From the various photographs of the spectrum of this 

 star, it appears that on September 23, 1887, the hydrogen lines 

 // and G are shown bright ; the star was then estimated as of the • 

 8th magnitude. On June 16, 1888, magnitude being estimated as 

 9, the spectrum was faintly visible and apparently continuous, but 

 no bright lines we^-e seen. On September 7 of the same year, 

 G was well seen, and h was barely visible, the magnitude being 

 again estimated as 8. There is no doubt, therefore, that this is 

 another example of that group of variable stars that exhibit 

 bright hydrogen lines in their spectra when at a maximum. 



Paris Observatory. — Admiral Mouchez, the Director of 

 this Observatory, has issued his Report for the year 1889. An 

 account of the resolutions adopted last September by the Inter- 

 national Committee for the execution of the map of the heavens 

 is given. It is also noted that the building is completed which 

 is to receive in two or three months the cotide equatorial, O'6o 

 metre aperture and 18 metres focus. M. Loewy has supervised 

 the details of the installation of this instrument, which will re- 

 place, with some advantage to Paris Observatory, the instru- 

 ment 074 metre aperture first intended for it. This latter 

 telescope is attached to Meudon Observatory, and will find there 

 atmospheric conditions more favourable for the use of its great 

 optical power than at Paris. 



The electric light has been installed for the lighting of the 

 two coude equatorials and the meridian circle. 



For some years, almost the whole force of the Observatory 

 has been engaged in re-observing on the meridian the stars in 

 Lalande's catalogue. This work was commenced about twenty- 

 five years ago, and on account of it other branches of astro- 

 nomy have had to be neglected. It is, however, nearly com- 

 pleted, and Admiral Mouchez proposes to the Council that a 

 regular spectroscopic service should be instituted. Up to now, 

 spectroscopy has only existed nominally at Paris Observatory, 

 and in appealing to the administration for the necessary funds 

 to organize this new department it is very truly observed that 

 no Observatory can well dispense with spectroscopic accessories, 

 since it is the study of this branch of astronomy that enables the 

 physical constitution of the heavenly bodies to be determined. 

 M. Deslandres, already known for his spectroscopic works, will 

 take charge of this new department. 



A Commission has been appointed to investigate the incon- 

 veniences that would arise from the laying of the proposed rail- 

 way line at a distance of about 150 metres from the Observatory. 

 The Report of the Commission, when ready, will have some 

 interest at other Observatories that have been similarly 

 threatened. 



MM. P. and P. Henry have continued the photographic work : 

 38 photographs of stars have been obtained, and 5 plates for the 

 determination of the parallax of Victoria. The constant of 

 photographic refraction has been determined, and lunar photo- 

 graphs having a diameter of 40 cm, have been obtained by 

 direct enlargement. 



Many observations have been made of comets. M. Bigourdan 

 has made 300 complete measures of nebulae ; the major planets 

 and the asteroids have received as much attention as the con- 

 tinued bad weather permitted ; and, leaving out of consideration 

 the absence of spectroscopic work, which another year may see 

 remedied, the Report is altogether a satisfactory one. 



On the Parallax of Double Stars. — At the March 

 meeting of the Royal Astronomical Society, Mr. Arthur A. 

 Rambant directed the attention of astronomers to a paper in 

 which he pointed out the relation connecting the parallax and 

 the relative velocity of the components of a double star with the 

 period and angular elements of its orbit, and discussed the possi- 

 bility of determining the distance by means of spectroscopic 

 observations of this velocity. The photographs of stellar spectra 

 recently obtained by Prof. Pickering in America and Prof. Vogel 

 at Potsdam are in point of accuracy so far in advance of direct 

 eye observations of motion in line of sight that they seem to 

 demonstrate the possibility of applying the method described to 

 the determination of parallax, and the author shows how the 



