122 PLEASANT WAYS /A SCIENCE. 



eventually became the brightest line of the whole spectrum 

 Comparing his own observations with those of Cornu, 

 Vogel points out that they agree perfectly with regard to 

 the presence of the three hydrogen lines, and that of the 

 brightest line of the air spectrum (belonging to nitrogen), 

 which is the principal line of the spectrum of nebulae. 

 This is the line which has no analogue in the spectrum 

 of the sierra. 



We have also observations by F. Secchi, at Rome, Mr. 

 Copeland, at Dunecht, and Mr. Backhouse, of Sunderland, 

 all agreeing in the main with the observations made by 

 Vogel and Cornu. In particular, Mr. Backhouse observed, 

 as Vogel had done, that whereas in December the greenish- 

 blue line of hydrogen, F, was brighter than the nitrogen 

 line (also in the green-blue, but nearer the red end than 

 F), on January 6 the nitrogen line was the brightest of 

 all the lines in the spectrum of the new star. 



Vogel, commenting on the results of his observations up 

 to March 10, makes the following interesting remarks (I 

 quote, with slight verbal alterations, from a paraphrase in a 

 weekly scientific journal) : " A stellar spectrum with bright 

 lines is always a highly interesting phenomenon for any 

 one acquainted with stellar spectrum analysis, and well 

 worthy of deep consideration. Although in the chromo- 

 sphere (sierra) of our sun, near the limb, we see numerous 

 bright lines, yet only dark lines appear in the spectrum 

 whenever we produce a small star-like image of the sun, 

 and examine it through the spectroscope. It is generally 

 believed that the bright lines in some few star-spectra 

 result from gases which break forth from the interior of 

 the luminous body, the temperature of which is higher than 

 that of the surface of the body that is, the phenomenon 

 is the same sometimes observed in the spectra of solar 

 spots, where incandescent hydrogen rushing out of the 

 hot interior becomes visible above the cooler spots through 

 the hydrogen lines turning bright But this is not the only 

 possible explanation. We may also suppose that the atmo- 



