56 A CENTURY'S PROGRESS IN ASTRONOMY. 



and now director of the Solar Observatory in 

 California, succeeded in photographing, by an 

 ingenious process, the whole of the chromo- 

 sphere, prominences, and faculse visible on the 

 solar surface. 



Another solar envelope was discovered in 1870 

 by Dr Charles Augustus Young, who from 1866 

 to 1877 directed the Observatory at Dartmouth, 

 New Hampshire, and from 1877 to 1905, that 

 at Princeton, New Jersey. During the eclipse 

 of December 22, 1870, Young was stationed at 

 Tenez de Frontena, Spain. As the solar crescent 

 grew apparently thinner before the disc of the 

 Moon, " the dark lines of the spectrum," he says, 

 " and the spectrum itself gradually faded away, 

 until all at once, as suddenly as a bursting rocket 

 shoots out its stars, the whole field of view was 

 filled with bright lines, more numerous than one 

 could count. The phenomenon was so sudden, 

 so unexpected, and so wonderfully beautiful, as 

 to force an involuntary exclamation." The phe- 

 nomenon was observed for two seconds, and 

 the impression was left on the astronomer that 

 a bright line had taken the place of every 

 dark one in the solar spectrum, the spectrum 

 being completely reversed. Hence the name 

 which was given to the hypothetical envelope 

 "the reversing layer." For long the existence 



