12^ 



approxi matei y monthly period, or to S[)eak more accurately, periods 

 differing only slightly from the anomalistic time of revolution, which 

 can also be taken as itiequalities of long period in the ecceiitricity 

 and the longitude of tiie perigee, and to the comparison of them 

 with the values found for the same by E. W. Brown in his new 

 lunar theory. 



My method was exactly the same as that used by Prof. E. F. 

 VAN DE Sande Bakhuyzen, ill his two papers in 1903, and previously 

 by Newcomb in his. "Investigation of coirections to Hansen's tables 

 of the moon". I also used errors in R. A. instead of those in longitude. 



Newcomb discussed the years 1862 — 1874, according to the obser- 

 vations made at Greenwich and Washington, and in a less tho- 

 rough manner the years 1847 — 1858 according to the Greenwich- 

 observations, while E. F. van de Sande Bakhuyzen treated the years 

 1895—1902 also by using the observations at Greenwich. As their 

 results pointed to terms in the eccentricity and the longitude of the 

 perigee of about an 18 years' period, nearly agreeing with the 

 Jovian evection as found by theory, it was natural for me te extend 

 the material discussed by van de Sande Bakhuyzen, so as lo cover 

 a period of 20 years. 



I began a preliminary mvestigation with a view to the then ap- 

 proaching solar eclipse of April 17^^ 1912. I used the observations of 

 the years 1907 — 1909 and the results of my calculations were published 

 in the Proceedings of tliis Academy 14, 1J80. On account of the 

 short period discussed, my investigation could yield no result of 

 general bearing. 



For this first investigation I had applied beforehand to Hansen- 

 Neavcomb's tables precisely the same corrections as Prof, van de Sande 

 Bakhuyzen had done and when later on I began to work after the 

 more extended plan, it was first necessary to consider if any change 

 needed be made in this. 



Prof, van de Sande Bakhuyzen had applied to the ditferences Aa. 

 which are given in the Greenwich-results in the sense calculation 

 minus observation, the following corrections : ') 



a. Corrections to the calculated mean longitude viz: 



1". periodic corrections 7idz = -{-!". 6d sin JJ -^0".1Q sin {D~(/) 



0".24 sin {D-\-g') + 0".09 sin <f — 0".33 sin ID — 0".21 sin (2D—g) ') 



1) Under the heading: "Comparison of the erroi's of the Moon from observations 

 by Transit and Altazimuth" corrections have been applied lo the A^ for the 

 motion of the moon in the intervd Lx itself, which are not yet taken into account 

 in other parts of the Results. 



~) In this the solar parallax was taken as t = 8".796. 



