34* 



NINETEENTH CENTURY. FT. ill. 



solar atmosphere in which the gases above mentioned have 

 been discovered. This atmosphere is supposed to be from 

 500 to 1000 miles high, and it has still another envelope 

 outside it. In 1842 a white light or corona was seen round 

 the sun when it was totally eclipsed by the moon, and red 

 flames were observed shooting up into it. We do not 

 even now know clearly what this corona is, but the red 

 flames or 'prominences,' as they are called, were studied 

 during the eclipse of 1868 by Professor Janssen in India, 

 and Mr. Lockyer in England, and they both saw two vivid 

 hydrogen lines (see No. 4, Plate II.), together with a third 

 line not yet well understood. The red prominences then 

 are made up chiefly of hydrogen gas, and Janssen and 

 Lockyer proved that they are jets from an envelope of this 

 gas which may be observed everywhere round the sun's 

 atmosphere to a height of 5000 miles. -To this envelope 

 Mr. Lockyer has given the name of chromosphere, which 

 has been generally adopted, and to him we owe a number 

 of important conclusions as to the sun's atmosphere, and 

 the nature of sun-spots and prominences, too lengthy to be 

 given in this work. 



It is only the bright light from the body of the sun which 

 prevents our seeing this hydrogen envelope at all times, and 

 Lockyer and Janssen discovered independently of each 

 other an ingenious way of making the hydrogen visible 

 even in broad sunlight. They passed the light through 

 many prisms at such angles that it was spread out till it 

 became very faint indeed, and then it no longer hid 

 the hydrogen lines, and they could be clearly seen. The 

 'red prominences' or ejections of brilliant incandescent 

 vapours from the chromosphere vary very much both 

 in their height and the time they remain. Some shoot 

 up 15,000 or 20,000 miles in a minute and fall back 



