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CAENEGIE INSTITUTION OF WASHINGTON. 



The question whether atmospheric haze and scattered Hght can 

 influence the results obtained in solar rotation observations has also 

 been examined by Mr. St. John. Observations were made with the 

 regular rotation apparatus and the 150-foot tower telescope, the hght 

 from a point 0.5 per cent of the radius outside the sun's limb being com- 

 pared with that from a point 1.5 per cent within the hmb, where the sUt 

 is set in the usual rotation observations. When the limb spectrum was 

 fully exposed, there was no trace of a spectrum from the light outside 

 the Umb, and a factor of about 100 in the exposure times was necessary 

 to obtain equality of densities. This is in agreement wdth the results 

 found by Mr. Abbot, who, from observations on the distribution of 

 Ught along the diameter of the solar image, concluded that the stray 

 Ught from all sources at a point 1.5 per cent of the solar radius outside 

 the limb is much less than 1 per cent of the sunlight at the limb for the 

 region of the spectrum employed in rotation observations. 



The measurement and reduction of the photographs required for 

 these investigations by Mr. St. John have been carried out by Miss 

 Ware and Miss Miller. Miss Ware has measured the solar-rotation 

 negatives, while Miss Miller has dealt with those used in the study 

 of the relativity efifect. 



INVESTIGATIONS OF STARS AND NEBULi«. 

 OBSERVING CONDITIONS. 



The weather conditions for night observations during the year 

 ending August 31, 1917, were somewhat below normal. This was 

 especially noticeable during the months of May and July, which were 



