138 ANNUAL REPORT SMITHSOIsriAN INSTITUTION, 1912. 



between the milky way and the great spiral nebulae a singularly 

 closer analogy than we had felt warranted in supposing until quite 

 recently. 



The new star discovered December 30, 1910, in the constellation 

 of the Lizard, has followed its predicted career, fading rather slowly. 

 It becomes more and more certain that temporaiy stars, even when 

 they show the ruddy aspect of certain periodic variables, show less 

 difference between the visual and photographic magnitudes. 



The polar star often used as a standard for photometric compari- 

 sons because it remams constantly at practically the same altitude, 

 seems to have abdicated that role and passed into the ranlcs of the 

 variable stars. In order to show its variability, Hertzsprung ^ 

 went through the discussion of 418 photographs, each having four 

 exposures. The variation amounts to 0.2 of a magnitude and takes 

 place in less than four days. 



II. 



The step from variable stars to the sun is very easy. It is espe- 

 cially so because of the recent work of C. G. Abbot.^ Measm^es upon 

 the intensity of the solar radiation made simultaneously on Mount 

 Wilson (1,800 meters altitude) and on Mount Whitney (4,420 meters) 

 gave very concordant results and the parallel march of the numbers 

 places beyond doubt a very decided variability of the sun which may 

 amount to a tenth of the total radiation witliin a few days. 



The work of Abbot tends also to show that the precision with which 

 we may state the temperature of the sun has been exaggerated. There 

 are in the sun sources of heat from 5,000° up to some 7,000°. How- 

 ever, the liigher temperatures predominate. The infra-rod radiation 

 comes from the deeper layers. 



Some years ago the researches of Halm appeared to indicate that 

 the rate of rotation of the sun, varying as we knew with the solar 

 latitude, varies also synclu'onously with the sun-spot cycle. The 

 mvestigation of this matter remains upon the program of the Edin- 

 burgh Observatory. But between the results obtained by Storey and 

 those by Adams at Mount Wilson there is a systematic difference. It 

 might be suspected that with one or the other the distance of the slit 

 of the spectroscope from the edge of the sun was not correctly deter- 

 mined. Or the cause of the discrepancy may lie iu the telluric oxygen 

 lines used for comparisons. 



The established l)ut not absolutely regular correlation which exists 

 between magnetic disturbances and the appearance of sun spots seems 

 to have been made decidedly clearer by the researches of Bosler, of the 



1 Astronomische Nachrichten, No. 4518. 



« Report of the Astrophysical Observatory of the Smilhsouian Institution. 



