PHYSICS NINETEENTH CENT.SPECTROSCOPY. 497 



be expected. The only known facts regarding them were that some of 

 them formed systems governed by the same laws of gravitation as 

 obtain in the solar system, and that analogy rendered it probable that 

 their constitution more or less resembled that of our sun. The lines 

 in the spectra of a few of the more conspicuous stars were described 

 by Fraunhofer in 1823. He observed the solar lines of D, E, b, and F 

 in the light reflected from the moon and planets. In the spectra of 

 the stars Capella, Betelgeux, Procyon, and Pollux he saw the D line, 

 and mentions the presence of the b line in the spectra of the first two. 

 Sirius and Castor exhibited lines altogether different from those of 

 the sun. It was not until about the period when Huggins and Miller 

 entered upon their researches that any further observations on star 

 spectra were published. Then some notices of stellar spectra appeared 

 by Donati of Florence, and about the same time as Miller and Huggins 

 laid the results of their first observations before the Royal Society, 

 Rutherford in America, Secchi in Italy, and Airy in England published 

 some diagrams of the lines in star spectra. 



Huggins and Miller found in the spectra of all the brighter stars 

 lines as fine and as numerous as those of the solar spectrum, and every 

 star sufficiently bright to exhibit a spectrum yielded one with lines, 

 which differed in their position and grouping for each star. In the 

 spectra of Aldebaran and of a Orionis the D line of sodium is visible, 

 and the lines marked b by Fraunhofer, which are known to be due to 

 magnesium. Four lines belonging to calcium were also observed in 

 both spectra. In the spectrum of Aldebaran, the two lines c and F, 

 indicating hydrogen, were conspicuous, in the spectrum of a Ortonis 

 they were altogether wanting. In the two stars upwards of 70 lines 

 were recognized, indicating the existence of certain known chemical 

 elements in those far-distant bodies. In Aldebaran, for instance, the 

 spectroscope gave evidence of hydrogen, sodium, magnesium, calcium, 

 iron, bismuth, tellurium, antimony, and mercury. 



In a preceding chapter we had occasion to mention the apparition 

 of a temporary star (page 85), and this is far from being the only 

 instance of such a phenomenon. Still, these instances are so rare, 

 that it may be esteemed a singularly happy chance that, while Huggins 

 and Miller were engaged in the observation of stellar spectra, a phe- 

 nomenon of this kind should occur. In May, 1866, a scarcely dis- 

 cernible telescopic star, T Corona Borealis, suddenly blazed out, and 

 became one of the most conspicuous stars in the heavens. Huggins 

 turned his instruments to this extraordinary object, and found that 

 its spectrum, differed remarkably from that of any other star he had 

 examined. It showed not only a spectrum with dark lines, but also 

 with bright lines, among which c and F, that belong to incandescent 

 hydrogen, were very conspicuous. The. inference that the increase of 

 brilliancy was due to intensely heated hydrogen, was irresistible. In 

 twelve or fourteen days this star, by gradual diminution of its sudden 



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