144 



Newcomb did not, however, take into account the possibility of 

 a constant error in the latitude, although he had himself previously 

 called attention to the want of foundation of Hansen's supposition 

 that the centre of gravity and the centre of figure of the moon 

 should not coincide in the direction of the radius vector. 



The intluence of a constant error in the latitude upon the R.A. is 



da sin ë 



— := COS X 



d^ COS^ (f 



or, as the greatest difference of coii^ ö from unity, for A = 90° or 

 270°, is 0.16, about 



da 



~ = — 0.40 cos X. 

 d^ 



We see therefore that, as we may neglect here the difference 



between mean longitude in the orbit and ecliptical longitude our term 



could, as regards its form, be completely explained by a constant 



error in the latitude and that the correction for this would have to 



be 4" l"-65, more than compensating Hansen's term — 1".0. As 



Bakhuyzen, from the declinations observed at Greenwich, after having 



freed them as far as possible from systematic errors, and reduced 



them to Newcomb's fundamental system, deduced a latitude-correction 



of only -\- 0".20, both from the observations of the limbs and from 



those of Mösting A, while in using the uncorrected declinations the 



correction would have been found to be zero or negative, it appears 



that if I, instead of using differences A«, had used the errors in 



longitude AA, calculated at Greenwich, 1 should have found an 



empirical term of about the same value. 



Astronomy. — On the sujnijicance of the term, in the Right 

 Ascension of the moon, found by J. E. de Vos van Steenwijk. 

 By Prof. E. F. vam de Sande Bakhuyzen. 



The most important result of the investigation of de Vos van 

 Steenwijk is doubtless the fact that the observations of the moon, 

 besides the inequalities theoretically determined by Brown, betray 

 the existence of a new ' term, apparently of an analogous form, 

 which was not explained by the theory. The reality of this term 

 might already be considered as established after his previous calcula- 

 tions; its existence and also the approximate accuracy of the co-ef- 

 flcients were put beyond all doubt by the determination of the 

 mean residual discordances remaining in h and k (see his second 

 paper), after they had been corrected on the one hand only for the 



