s66 



NA TURE 



[October 1 1, 1894 



one pages. In the preface, the author accounts for this 

 by pointing out that the present state of our knowledge 

 of the constitution of the sun is unsatisfactory, and that 

 we have " a large mass of observational data, although 

 for the most part unscientifically discussed ; and on the 

 other hand, an indefinite number of hypotheses and solar 

 theories, which are, with few exceptions, radically wrong 

 at the start, and often contradictory to the most simple 

 physical views of to-day." He therefore felt unwilling to 

 undertake the task of discussing and sifting these theories. 

 No doubt an author has a perfect right to decline an un- 

 congenial task, but it certainly detracts from the value of 

 the book that it gives comparatively scant information 

 about our central luminary, on which spcctroscopists 

 have spent so much labour ; and in the succeeding 

 chapters Dr. Scheiner has by no means been adverse to 

 dealing with '• hypotheses and theories." It is, of course, 

 as impossible to discuss the results of spectroscopic 

 observations without attempting to interpret them, as it 

 was for our forefathers three hundred years ago to dis- 

 cuss the motions of the planets " without any hypo- 

 thesis.'' And notwithstanding his caution, the author 

 has not been able to keep clear of questionable hypotheses 

 on matters connected with the sun, as when he, for in- 

 stance, suggests that the unsymmetrical broadening of 

 lines in spot-spectra might arise from the metals entering 

 into combinations with the metalloids. This idea is also 

 afterwards brought in to account for the same pheno- 

 menon in star-spectra of Type Ilia, but Dr. Scheiner 

 seems lately to have abandoned it, as he in a note to 

 p. 30S concludes from recent observations that the un- 

 symmetrical broadening is due to accidental "clustering" 

 of fine lines. With regard to the spectra of sun-spots, 

 we notice that all the work done at South Kensington is 

 completely ignored. 



While the chapter on the spectra of the planets, as to 

 which not much work has been done of late years, is 

 naturally somewhat meagre, that on comets is very full 

 and interesting, and includes an account of the important 

 laboratory work of Hasselberg. The evident dependence 

 of the spectrum on the distance of a comet from the sun 

 is duly emphasised, but the account of the two most re- 

 markable comets of 1SS2 might have been more lengthy, 

 as we, for instance, do not find any reference to the 

 dark absorption lines seen with more or less certainty by 

 several observers, and which (if really existing) are of 

 very great importance for the interpretation of the 

 changes in the heads of comets about the time of peri- 

 helion passage. 



In the chapter on Nebula;, a complete list of gaseous 

 nebulx is given, as well as one of the minute planetary 

 nebulx found with the spectroscope by I'ickering and 

 Copeland, and it is interesting to see how this latter 

 class of objects, like the older gaseous nebula:, cling to 

 the Milky Way. A list is also given of all the lines 

 observed in the spectra of nebulx. It might have been 

 mentioned that the line at 4472 (which also occurs in 

 some stars of Type la and in Nova Auriga;) is probably 

 identical with a well-known chromospheric line, asso- 

 ciated with Dj and the hydrogen lines, as suggested by 

 Mr. Lockyer. The author does not express any opinion 

 as to whether the temperature of nebuUe is high or low, 

 but he remarks that the comparative simplicity of the 

 NO. 1302, VOL. 50] 



spectrum points to the conclusion that the density of 

 these bodies is extremely low. 



In the lengthy chapter on the spectra of the stars, the 

 classification of \'ogel is followed, apparently somewhat 

 reluctantly on the part of the translator. So long as the 

 system is not supposed to represent the gradual evolu- 

 tion of a star, there can, of course, be no objection to it ; 

 but in the light of the results obtained from temporary 

 stars, and the detection of dark lines in spectra of 

 Type \c, it certainly looks doubtful if the bright line stars 

 can properly be divided among the two first classes (If 

 and \\b). 



The account of spectra of Type \a includes a list of 

 ninety-one lines measured by the author in the photo- 

 graphic spectrum of Sirius, and an account of the 

 harmonic relations between the hydrogen lines. That 

 the stars of this class are the hottest of all, is generally 

 conceded, and the confirmation of this view, which Dr. 

 Scheiner (in a note on p. vii.) finds in the appearance of 

 the magnesium line at 44S1, was indeed found many 

 years ago by Mr. Lockyer {JProc. R.S. xxx. p. 29), who 

 first called attention to the fact that this line can only be 

 produced by a high tension spark, and is indicative of 

 very high temperature. In the spectrum of « Cygni (Typej 

 \b) it is the strongest of all lines. Notwithstanding this 

 the author concludes from the fact that only the fainter 

 iron lines occur, that a very different temperature must! 

 prevail in stars of Type \b from that in stars of \a. Vci 

 the possibility does not seem to be excluded that this may 

 arise from different conditions as to density. Under the | 

 heading " Spectra of Type L," the translator gives 

 detailed account of Belopolsky's investigation of ,i L\i 

 with regard to which Dr. .Scheiner remarks in a note 

 that, in view of recent observations made at Potsdam, he 

 cannot believe the phenomenon 10 be nearly as simple as 

 Belopolsky's observations would indicate. " There is 

 great probability that more than two bodies are con- 

 cerned in the case of /3 Lyra:." 



Passing to the Type II<7, we find a catalogue of ; 

 lines measured by the author on Potsdam pliotographs 

 of the spectrum of . I Aurigx". While the authoi justly con- 

 siders this a complete proof of the absolute agreement 

 between the spectrum of this star and that of the sun, he 

 takes a very pessimistic view of the measures of the visual 

 spectrum of « Tauri by Huggins and Vogel, whose identi- 

 fications of lines with metallic lines he seems, with few 

 exceptions, to consider worthless. Many readers will 

 probably dissent from this view, as the agreement between 

 the two observers is really good (as also concedeil by the 

 author), and this somewhat sweeping condemnation would 

 apparently, if consistently applied, wipe out many con- 

 clusions drawn from spectroscopic observations. 



In the section " Spectra of Type 11/'" the translator 

 has put together a large amount of information not to bei 

 found in the original, by giving a list of fifty-five stars of 

 this class (which are with few exceptions in or close to the! 

 Milky Way), and a list of bright lines in the visual spectra 

 of thirty-one of them, recently observed by Campbell at 

 the Lick Observatory. The existence of a large envelope' 

 of incandescent hydrogen about one of these stars 

 (D.M. -f 30 , 3639) seems to be proved by Campbell's | 

 latest observations, according to which the Fline,ob5erved 

 with a narrow slit, is a long line extending to a very ap- 



