141 



Our result 0".26 hir^ei-, is thus in moderate accordance with the 

 theory. 



As regards the [)eriodic terms, it is very satisfactory that Brown's 

 inequalities are so well contirmed by the observations. It is, however, 

 remarkable that after Bkoavn's thorough investigations the observations 

 still betray an inec|uaUty with a coefticient of 0".66, which is theo- 

 retically unexplained. 



Still I think that we are driven to this conclusion, and that the 

 supposition of E. F. Bakhuyzen (Proc. Akad. Amsterdam 6 1903, 

 417), when he could find no trace of the existence of Brown's term 

 I (= Radau I) in the observations, that in the yeai-s considered 

 another term must have neutralized its effect, is fully confirmed. 

 For we now find that with equal coefficients their arguments in 

 1863 differed by 180°. 



Astronomy. — Investigation of the inequalities of a.pproximately 

 monthly period in the longitude of the moon, according to 

 the meridian observations at Greenwich. 2"^^ part. By J. E. 

 DE Vos VAN Steenwijk. (Communicated by Prof. E. F. van üe 

 Sande Bakhuyzen). 



In connection with my previous paper on the inequalities in the 

 longitude of the moon, the period of which differs little from the 

 anomalistic period of revolution, I have made some further calcu- 

 lations. 



Even after applying the corrections which we have discussed 

 and all the new inequalities determined by Brown, a discordance 

 still remained between observation and theory, which could be 

 expressed by the following empirical term to be added to the 

 theoretical longitude : 



+ 0".66 siu y 4- 244°.4 + 40°. 35 (^— 1900.0)j 

 I have already pointed out that it is striking that an inequality 

 with such a comparatively large coefticient should exist, which is not 

 explained by theory, and on this account I have tried to establish 

 the reality of this term with greater certainty. 



For this purpose first the value of this term and its influence 

 upon h and k were calculated for each year, and my — Ay and 

 — X'y were corrected for this. After this the mean residual dis- 

 cordance in ho and ku Was determined, and in the second place 

 for comparison the same was done, when h^ and k„ were not 

 corrected for the empirical term. In the third place the same 



