110 LIGHT SCIENCE FOR LEISURE HOURS. 



ing spectacle, truly, but so short-lived that no man can 

 ever hope, though he lived to four-score years and ten, 

 to let his eyes rest in all his life for more than ten or 

 twelve seconds on the beautiful array of coloured lines 

 which two men only have as yet beheld. We may in- 

 crease the dimensions and power of our telescopes until 

 the existence of these lines can be recognised without 

 the aid of eclipse-darkness, but the lines can never be 

 seen, save during eclipse, as Young and his colleague 

 saw them last December. And these observers tell us 

 that in a second or two the lines vanished, the ad- 

 vancing moon hiding the shallow solar atmosphere. If 

 it should ever be given to any man to see six total 

 eclipses (which has never yet happened to any), and to 

 successfully apply in each instance the method em- 

 ployed by Professor Young, then in all, during his life, 

 that man would have seen the beautiful line-spectrum 

 to perfection for some ten or twelve seconds ; but not 

 otherwise can even so long a total period of observation 

 be secured. No single observer, then, can hope to 

 lear^i much about the thousands of lines which have 

 still to be mapped during eclipse opportunities. 



But now let us consider the import of the observa- 

 tion. What are these myriads of coloured lines? 

 Every dark line of the solar spectrum, says Professor 

 Young, seemed to have its representative in this 

 bright-line spectrum. Many of the groups of lines 

 which had flashed so quickly into view and endured 

 but so brief a period, were familiar to him ; in other 

 words, his study of the solar spectrum had made him 



