60 



of the gas of iron, over 400 in number, had their coun- 

 terpart in dark solar lines, and from that time the pres- 

 ence of various other substances in a gaseous state has 

 been detected. The method of using the spectroscope is 

 simply to examine the spectrum of any substance and 

 compare it with known spectra. 



The truth of the theory that the sun is a vast globe 

 probably solid at an immense heat, surrounded by a gas- 

 eous layer, has received wonderful confirmation in recent 

 eclipses. If the dark lines in the solar spectrum are 

 merely the bright lines of certain gaseous substances 

 made dark by the presence of the glowing body behind 

 them, it must follow that just before totality, when the 

 moon has wholly concealed the body of the sun but not 

 the gaseous layer, the dark lines should become bright. 

 The reversal of the lines, looked for without success in 

 1869, was seen in 1870 by Prof. Young, who thus de- 

 scribes the phenomenon : 



" Very soon as the crescent grew narrower, .... 

 the dark lines of the spectrum and the spectrum itself 

 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. Gently and yet very rapidly they faded 

 away, until within about two seconds, as nearly as I can 

 estimate, they had vanished." This phenomenon has 

 been seen by many observers in recent eclipses. 



As the solar prominences can now be examined upon 

 any clear day, they receive less attention during eclipses 

 than the corona, which in the present state of science is 

 only visible at such times. The coronse of different 

 eclipses are so dissimilar in appearance, and the results 



