150 



ASTRONOMICAL PHENOMENA AND PROGRESS. 



Mr Covey gives an account of a comet first 

 seen by him, November 21st, preceding, in 

 declination, nearly 15 N., and right ascension 

 200. On that date, it had the size of a star of 

 the third magnitude ; its course was afterward 

 found to be northeastwardly, from Arcturus 

 toward Vega in the Harp ; its brilliancy was 

 diminishing, and it soon became invisible to 

 the naked eye. Messrs. Silliman and Dana say 

 there is hardly a doubt that this was the comet 

 described by Prof. "Watson, and detected (it 

 now seems), a few days previously (Dec. 28th, 

 1863,) by Respighi, of the University of Bolo- 

 gna. The most remarkable circumstance in the 

 case is, that a comet visible to the naked eye 

 should be present in the heavens a full month 

 before its discovery was made at any observa- 

 tory ; but it was visible at about five o'clock 

 A. M., an hour when most astronomers have 

 concluded their labors. 



Spectra of Fixed Stars, Etc. The results thus 

 far arrived at in the way of determining the 

 character of the spectra of different fixed stars, 

 and others of the heavenly bodies, and hence, 

 by inference, their physical and chemical consti- 

 tution, are as yet to some extent at variance. 

 This, indeed, was to be expected in the outset 

 of observations of so extreme delicacy, conduct- 

 ed by different persons, with different forms of 

 apparatus, and under differing conditions of the 

 terrestrial atmosphere. Prof. Donati finds, in 

 the case of nearly all the stars which have 

 been examined both by M. Franenhofer and 

 himself, different systems of fixed lines from 

 those originally laid down by the latter ; and 

 some differences, again, exist between the sys- 

 tems given by either of these and the spectra 

 of the same stars as noted by M. Secchi in It- 

 aly, by Mr. Rutherfurd in New York, and by Dr. 

 W. A. Miller and Mr. Wm. Huggins in England. 



Frauenhofer had not condensed upon his 

 prism the light of the star to be examined, 

 but placing the prism and a cylindrical lefts be- 

 fore the objective of a small (observing) teles- 

 cope, he directly viewed the spectrum afforded 

 by analysis of the light, of such intensity as it 

 naturally fell upon the apparatus. The cylin- 

 drical lens was to supply the place of the fine 

 slit between knife-edges first employed for the 

 solar spectrum by Wollaston ; such a lens act- 

 ing to elongate the image of the star in one 

 direction only, or to a line, and giving to the 

 spectrum the desired breadth without increas- 

 ing its length. 



Mr. Rutherford (" American Journal of Sci- 

 ence," Jan. and May, 1863) states that through- 

 out the course of his observations he received 

 the light through a slit on its way to the prism ; 

 but that, finding that the necessity of throwing 

 the star slightly out of focus occasioned a con- 

 siderable loss of light upon the jaws of the 

 slit, he was later led to add to the arrangement 

 the use of the cylindrical lens introduced be- 

 tween the objective of the condensing teles- 

 cope and the prism and with the effect of 

 largely increasing the light, and, of course, the 



distinctness of view of the parts of the spec- 

 trum obtained. The lens is useful only in the 

 analysis of merely luminous points, as the stars 

 may be assumed to be, and not in case of the 

 planets, sun or moon. Excepting the addition 

 now named, the spectroscope was simply that 

 of Bunsen andKirchhoff, " consisting of a con- 

 densing telescope with adjustable slit, a scale 

 telescope with photographed scale of equal parts 

 showing bright lines upon a dark ground, a 

 flint-glass prism of 60, and an observing teles- 

 cope with Huyghenian eye-piece, magnifying 

 about five times." If the telescopes be not 

 perfectly achromatic, some change of focus 

 will be required in order favorably to observe 

 the different regions or colored spaces the ul- 

 tra-red rays requiring a slight, and the violet 

 and indigo a considerable, change of focus 

 from that answering for the intervening por- 

 tion of the spectrum. For exact comparison of 

 different observations, the place of the sodium- 

 line D was, in each instance, brought to coin- 

 cide with the division of the scale marked 30. 



With the* apparatus so adjusted, the locations 

 of the seven principal lines of the spectrum of 

 sunlight, as determined by Mr. Rutherfurd, are 

 as follows (the letters reading of course, from 

 red to violet) : B 33.1, C 32.3, D 30, E 27, 26.5, 

 F 24.4, G 19.3, H 14.5. 13.9. By means of a 

 plate (highly valuable for reference) he gives a 

 comparative view of the spectra of the sun, 

 moon, Jupiter, Mars, and 17 of the brighter 

 among the fixed stars. In the lunar spectrum 

 he finds the principal solar lines, B, C, D, E, 

 and F, and he supposes that G may yet be de- 

 tected. The lunar lines just named are very 

 strong and well defined; and other marked 

 features are beyond F, a broad faint band at 

 21.05,a broad line at 19.9, and a broad dark line 

 at 18.09. 



Most noticeable in the spectrum of Jupiter 

 are the distinct line D, and two broad bands 

 respectively at 32.1 and 31.12 ; in that of Mars 

 D is wanting, though there is a well-defined 

 line near its place, at 30.25, other strong lines 

 at 27.1 and 26.55, and a broad band at 24.4. 



Without attempting to fix upon any final 

 principle of classification for the stars he has 

 examined, Mr. Rutherfurd for the present di- 

 vides their spectra into three groups: "first, 

 those having many lines and bands, and 

 most nearly resembling the sun viz., Capella, 

 /3 Geminorum, a Orionis, Aldebaran, y Leonis, 

 Arcturns, and/3 Pegasi. These are all reddish 

 or golden stars. The second group, of which 

 Sirius is the type, present spectra wholly un- 

 like that of the sun, and are white stars. The 

 third group, comprising a Virginis, Rigel, etc., 

 are also white stars, but show no lines ; per- 

 haps they contain no mineral [query metallic ?] 

 substance, or are incandescent without flame." 

 Taking Capella and Sirius as good examples of 

 the first two classes of stars just named, their 

 spectra are thus described : Capella a line 

 respectively at 30.22, 27.73, 27.38, 26.75 and 

 24.78 ; Sirius a broad black line, or band, 



