CH. xxxiV. 7 HE SOLAR SPECTRUM. 343 



like jets of water ; others remain for some days, and Respighi 

 tells us that they reach a height of 80,000 miles or more. 

 Thus we have evidence in the sun of a photosphere, or lumi- 

 nous body, in the centre, an atmosphere of cooler gases round 

 it which absorbs part of its light and causes the dark lines 

 in the spectrum, and a chromosphere or coloured sphere of 

 hydrogen gas which throws out jets of enormous height into 

 a corona, the nature of which is as yet very imperfectly under- 

 stood. The spots on the sun which Galileo noticed have also 

 lately been much studied, especially by De la Rue, Balfour 

 Stewart, and Loewy : they appear to be hollows which open 

 from time to time in different places in the body or photo- 

 sphere of the sun. We cannot discuss them here, but spec- 

 trum analysis has helped to prove that they are depressions. 



The solar spectrum has now been mapped out with 

 wonderful accuracy, and the name of Professor Angstrom, 

 of Sweden, will always be remembered as one of the most 

 able workers in this path. 



Dr. Huggins and Dr. Miller examine the Stars by 

 Spectrum Analysis, 1862. Only a few months after 

 Kirchhoff had proved that the black lines in the solar spec- 

 trum reveal to us what elements exist as gases around the 

 sun, two English chemists, Dr. Miller, who died a few years 

 ago, and Dr. Huggins, who is still living, began to try the 

 same experiments with the other heavenly bodies. 



Their instruments were now much more perfect than 

 those which Fraunhofer had used, and they were able to see 

 the effects of our own atmosphere upon sunlight. When 

 the sun is setting and its light has to pass through a long 

 layer of air before it reaches us, faint lines appear on the 

 spectrum, because some light is absorbed by the watery 

 vapours in our atmosphere. Now, when Miller and Huggins 

 examined the light which conies from Jupiter, they found 



