president's^ ADDRESS SECTION A. 83 



and Dr. Huggins'^ thought that it would be possible, by using 

 absorbing media, to keep out the other rays, and that it would be 

 possible to photograph the corona by the part between G and H. 

 The importance of this will be seen when it is remembered that the 

 eclipsed sun is only visible about eight days in a century, and then 

 only from small and inconvenient areas of the earth's surface, and 

 even this small chance is again limited by cloud and possibly in- 

 accessible positions on the earth's surface. The possibility of 

 making an artificial eclipse such that the sun's surroundings could 

 be photographed at any time Avas a problem worth working at, and 

 Dr. Huggins", with characteristic energy, threw himself into it, 

 and succeeded by using absorbing media in getting faint but un- 

 mistakable photographs of the corona ; the available media were 

 insufficient for better results. 



In 1866 and 1868" he had tried by the same method to see the 

 prominences, but met with only partial success for want of more 

 suitable media. He had, however, in 1867'''', by means of absorb- 

 ing meJia, insulated the spectra of different parts of the sun's 

 surface, such as the spots and the umhrce of spots. The photo- 

 graphs of the corona taken by Dr. Huggins about the time of the 

 eclipse of May 17 th, 1868, were examined by Captain Abney, who 

 said that '• not only were the general features in thern the same as 

 in those taken by himself in the actual eclipse in Egypt, but also 

 that details, such as rifts and streamers, have the same form and 

 position," but the absorbing media were not satisfactory, and he 

 subsequently used a reflecting telescope and chloride" of silver 

 as a sensitive surface, which is sensitive only to violet rays. With 

 this some success was attained, but not enough to satisfy Dr. 

 Huggins, and the work was given up, although he felt " that 

 problems of the highest interest in the physics of the sun are 

 doubtless connected with the varying forms of coronal light, which 

 only seem to admit of solution on the condition of its being possible 

 to study the corona continuously." From fifty photographs of 

 the corona which Dr. Huggins had taken in this way during 

 May, Mr. Wesley was able to prepare a number of drawings of the 

 corona. 



In 1883 Professor Pickering'® designed a star camera with the 

 object of making regular comparisons of star magnitudes. It 

 was so arranged that the whole heavens from 30° south to 60° 

 north and over three hours of right ascension coald be photo- 

 graphed on one plate measuring 6in. x 8in., which was divided into 

 six parts or pictures, all of which could be taken in eighteen 

 minutes. The great facility such an arrangement affords f(n- com- 

 paring star magnitudes is obvious, and the result has fully justified 

 the time given to it. 



For some years before his death (in 1882) Dr. H. Draper had 

 devoted himself to the study of stellar spectra, and his death for a 

 time put an end to this important work, but it was subsequently 



