Jan. 9, 1890] 



NATURE 



233 



The principal line in the photographic spectrum is near wave- 

 length 373, and this seems to be special to certain parts of the 

 nebula, according to Dr. Huggins s researches. 



Although so much admirable work has already been done, 

 there is still abundant scope for further investigations. One of 

 the chief points requiring attention at present is the character 

 of the brightest line, near A 500. Researches on the spectra of 

 meteorites, coupled with previous records of the line as having 

 a fringe on its more refrangible side, led Prof. Lockyer to sug- 

 gest, in 1887, that it was the remnant of the fluting near A 500 

 seen in the spectrum of burning magnesium. Observations 

 liave since been made by Prof. Lockyer, Mr. Taylor, and 

 myself, and all agree that the line is not sharp on the more re- 

 frangible side. Further observations are suggested. High dis- 

 ]iersion is not necessary, or indeed desirable. 



Direct comparisons of the chief nebula line with the mag- 

 nesium fluting are also required, but this is an observation of 

 preat delicacy, requiring high dispersion. It must also be 

 (iLMBonstrated that under the same conditions of comparison the 

 K line of hydrogen is coincident with the third nebula line. 



It has been suggested that the line near 559 recorded by Mr. 

 Taylor is the remnant of the brightest manganese fluting ; this 

 can only be decided by direct comparisons. 



In my own observations I noted that the F line is not seen 

 in all parts of the nebula, and in this respect it resembles the 

 ultia-violet line. This localization of the lines opens up a new 

 lield of work. 



(2) This is one of the finest examples of stars of Group II. 

 The bands i to 9 are perfectly well seen, but there is no 

 record of the presence or absence of line absorptions. Observa- 

 tions of the carbon flutings are suggested, a spirit-lamp flame 

 being convenient for comparisons. The two flutings to be 

 examined, both for position and compound structure, are those 

 near A 517 and 474. The latter is a group of five flutings, 

 extending from about A 468 to A 474, and under some conditions 

 the point of maximum brightness of the group is shifted from 

 474 10468. Comparisons of bands 4 and 5 with the brightest 

 flutings of manganese and lead should also be made. 



(3) This is a star with a spectrum of the solar type, of which 

 the usual differential observations are required. The relative 

 thicknesses of the hydrogen and other lines should also be 

 noted. 



(4) Gothard describes this star as belonging to Group IV. 

 The usual observations are required. 



(5) This is a star of Group VI., in which band 9 is dark, and 

 band 6 pale. Duner does not record any of the secondary 

 bands. These and absorption lines should be looked for. 



(6) This variable has a period of 423 days, and ranges from 

 8'5 at maximum to I3'5 at minimum (Gore). The spectrum 

 has not yet been recorded. Maximum on January 9. 



(7) This is a variable with a spectrum of the Group II. type. 

 The period is 324 days, and the magnitude varies from about 8 

 at maximum to 9*5 at minimum. The maximum will not occur 

 until January 17, but observations for the bright lines of hy- 

 drogen, &c., may be commenced at once. Variations of the 

 widths and intensities of the bands before and after maximum 

 may also be looked for. A. Fowler. 



Identity of Comet Vico (1844) with Brooks's (1889). — 

 In a note on some comets of short period {^Bulletin Astj-onoinique, 

 November 1889), M. L. Schulhof observes that a comparison 

 of the elements of Vice's comet (1844) given by Le Verrier with 

 those of Brooks's comet (1889) shows a striking similarity. 

 According to Mr. Chandler {Astronomical Journal, No. 205), 

 Brooks's comet in May 1886 was at a distance 0^064 from 

 Jupiter, and in heliocentric longitude 185°, whilst Vico's comet 

 found itself about 1885-86, according to the elements of M. 

 Briinnow in heliocentric longitude 162°, and approximately 0*4 

 from Jupiter. M. Schulhof adds, however, that the only objec- 

 tion to the hypothesis is that the aclion of Jupiter at a distance 

 o"4 would hardly have been sufficient to change so considerably 

 the perihelion distance and the time of revolution. It will be 

 sufficient to calculate back the perturbations of Brooks's comet as 

 far as 1885 to definitely settle this question. 



An investigation of the elements of Comets Lexelland Finlay 

 has led to the conclusion that they are not identical, but the 

 results found are not to be taken as conclusive, a farther and 

 more exact determination of the elements of Finlay's comet 

 having been undertaken. 



Observations of some Suspected Variables. — Observa 

 tions of Lalande 26980 = I4h. 427m, -H 6" 28'-9 (1875), be 

 Rev. John G. Hagen, of Georgetown College, give the n^ativy 

 result that there is no proof of variation between the years 1884- 

 89, and although an average of 15 observations a year have been 

 made, the extreme range of magnitude is less than o'2. 



Three stars were found that showed rather a large difference 

 from the Bonn D. M. magnitudes, and were watched from 1886 

 to 1889. No variation, however, was noticed during these 

 three years. The following are the three stars and the magni- 

 tudes found compared with A rgelander's : — 



D.M. 55-2587 

 D.M. 44-3368 

 D.M. 44-3402 



78 db o-i ; D.M. = 8-8. 

 7-6 i'o'i ; D.M. = 7-0. 

 77 ± o-o; D.M. = 8-1. 



Spectrum of a Metallic Prominence. — Prof. Vogel in 

 a letter to Prof Tacchini {Mem. Societa Spettroscopisti Italiani, 

 November 1889) observes that the positions of the lines 

 measured in a metallic prominence on June 28 were incorrectly 

 given by Prof. Spoerer in the Memorie for October (see Nature, 

 vol. xli. p. 115), and that the following should be substituted : — 

 Wave-length. Origin. Wave-length. Origin. 



667-6 Fe I 553-4 Ba, Fe, Sr. 



C H. I 531-6 Ceronium. 



649-6 Ba. 5269 Ca, Fe. 



646-2 Ca. 518-8 Ca, Fe. 



Di Na, b^ Mg. 



D2 Na. I b^ Mg. 



D3 Helium. b^ Fe, Ni. 



b^ Mg, Fe. 



The above table only contains a small number of the bright 

 lines seen in this eruption. 



Comet Swift (/ 1889, November 17). — The following 

 corrected elements are given by Dr. Zelbr {Astr. Nachr.y 

 2944) :— 



T = 1889 November 29-664x1 Berlin Mean Time. 



The brightness on Jan. 8 = 0-48 and on Jan. 28 = 0-30, 

 that at discovery being taken as unity. 



M. Schulhof notes {Bulletin Astronomique, November 1889)- 

 that, according to the elements of this comet, it is probably 

 identical with Blanpain's comet (1819), which M. Clausen has 

 shown to be identical with Grischow's comet (1743). 



Solar Spots and Prominences. — In the November 

 Memorie della Societa degli Spettroscopisti Italiani, Prof. Tacchini 

 contributes a note on spots and faculae observed from July to 

 September of this year. A comparison of these observations 

 with those of the preceding quarter shows an augmentation of 

 the phenomena described and a diminution of the frequency of 

 days without spots. 



Spectroscopic observations made by Prof. Tacchini during the 

 same period as the above show the mean daily number of 

 prominences to have been 2-93, with an average altitude of 



