i88 SCIENCE PROGRESS 



search, shows that the single gas which by its luminosity 

 proclaims nebulae in widely separated regions of the vast 

 universe cannot yet be identified with any known element. 



In his study of the spectrum of Nova Coronae Borealis 

 which blazed forth in 1866, Huggins was able to discover the 

 peculiar feature which has been found to be characteristic of 

 all the new stars that have since appeared. They are marked 

 in the early stages of their appearance by a spectrum in which 

 the characteristic feature is a number of bright lines each 

 accompanied by a dark line on the side of shorter wave-length. 

 The lines are in reality too broad to be called lines, and so free 

 from structure that one hesitates to call them bands. 



In the later stages of decline of a Nova, the spectrum changes 

 and gradually assumes the characteristics of the spectrum of 

 a planetary nebula. When the Nova appeared in the con- 

 stellation of Auriga in 1892, Sir William Huggins was able 

 to observe it with new apparatus of increased power and 

 refinement; his observations contributed in no| small degree 

 to our knowledge of the peculiarities of the spectra of new 

 stars. When the star had faded away to 14th magnitude and 

 more, he had taken the opportunity to have certain necessary 

 alterations made to the eye end of his telescope and so was 

 debarred from taking part in the earlier observations of the 

 second stage of brightness, which occurred in August 1892, 



But v/hen it was discovered by Campbell and others that the 

 spectrum had changed and had taken on the characteristics of 

 the spectrum of a planetary nebula. Sir William Huggins was 

 able to sound a note of caution. For in February 1893, by 

 visual observations of this star of 9th magnitude made with 

 a grating spectroscope, he was able to detect structure in the 

 lines which approximately coincided with the nebular lines. 

 This structure extended over a range of wave-lengths more than 

 a hundred times as great as the width of the ordinary nebular 

 lines ; and though time showed that the spectrum eventually 

 reached a stage which justified Campbell's surmise, there were 

 few astrophysicists who did not marvel at the delicacy and 

 acuteness of observing power by which Sir William and Lady 

 Huggins had succeeded in detecting visually features which 

 even the photograph had difficulty in portraying. 



In 1868 Huggins communicated to the Royal Society his 

 memorable paper on the measurement of motions of recession 



