REPORT OF EXECUTIVE COMMITTEE XXI 



.Simon Newcomb, Washington, D. C. Grant No. 17. For deter- 

 mining the elements of the moon' s motion and testing the law of 

 gravity. $3,000. 



Much of the material for this investigation, consisting of computa- 

 tions of places of the moon from Hansen's tables and their compari- 

 son with observations, was preserved in the archives of the Nautical 

 Almanac Office, waiting an opportunity for their working up. By- 

 permission of the Secretary of the Navy, Hon. William H. Moody, 

 these papers were entrusted to the Carnegie Institution and by the 

 Institution to Professor Newcomb. 



Abstract of Report. — The importance of this work grows out of the 

 fact that new tables of the moon are urgently required for the pur- 

 poses of astronomy and of navigation. For a long period the prob- 

 lem of constructing and perfecting such tables has been delayed by 

 an unexplained discordance between the observed motion of the 

 moon and the motion which should result from the action of all 

 known bodies upon it. The exact cause of this discordance cannot 

 be recorded, because the observations from 1750 to 1850 have never 

 been worked up and compared with the tables. The problem of 

 determining the exact nature of the deviation of the moon from its 

 predicted place is twofold. The observations since 1750 must be 

 worked up, and in order to compute the comparison the action of 

 the planets on the moon must be recomputed with a view to deter- 

 mining whether any correction to the past computations is necessary. 



By aid of a grant from the Carnegie Institution an important term 

 of long period, produced by the action of Venus, has been recom- 

 puted. 



Professor Newcomb has taken up the work on the adopted plan 

 of the occultations of stars by the moon, a work that he had begun 

 in connection with the Nautical Almanac. This, in connection with 

 the incorporation of other important observations, can probably be 

 completed in two years more. 



E. C. Pickering, Harvard University, Cambridge, Mass. Grant No. 

 20. For study of the astronomical photographs in the collection of 

 Harvard University. $2,500. 



Abstract of Report. — The grant made to Professor Pickering was 

 applied to a great variety of uses. These included sums paid to 19 

 different assistants and computers, and for other assistance in con- 

 nection with the Harvard Observatory. 



