A . dp 



A;i .sme = — , 

 dt 



where p is the quantity so called by Mr. Woltjeu. We thus find 

 for the three hypotheses 



Seeligkr AA = -f 0".47 



A + 1 .13 



C +0.15 



Newcomb did not include a deviation between observation and 

 theory for this quantity. At the time of the publication of the 

 "Astronomical Constants" (1895) it was of course entirely correct 

 to consider a determination of the planetary precession from obser- 

 vations as impossible. Since that time however very accurate invest- 

 igations of the precession have been executed by Nrwcomb himself 

 (Astr. Papers, Vol. VIII) and by Boss (Astr. Journal, Vol. XVI, 

 Nrs. 612 and 614). Now the precession in right-ascension depends 

 on the planetary precession, but that in declination does not. We 

 have 



m =z Z cos E — ?. 

 n = I sin e 



I being the lunisolar precession. 



Newcomb determined / tVom the right-ascensions and tiie declina- 

 tions separately, and found a large difference in the results. If this 

 were interpi-eled as a correction to the |)lanetary precession, we 

 should find 



Aa=: + 0".47. 



Boss determined vi and n separately, the latter both from right- 

 ascensions and from declinations. From his results I find (applying 

 the correction of the equinox /\e = -|- 0' .30, adopted by both Boss and 

 Newcomb) : 



AA = + 0".85 ± 0".22 



The mean error does not contain the uncertainty of the correction 

 Ae. Its true value probably is about = + 0".25. The mean error 

 of the value of A;, derived from Newcomb's work is difficult to 

 estimate; we may assume it to be equal to that of Boss. The mean 

 of the two determinations would then be 



a;, irr + 0".66 d= 0".18^). 



') Also L. Struve (A. N. Vol. 159, page 383) finds a diflerence in the same 

 sense. Neglecting tlie systematic correction v, 1 find from his results 



A'. = + 0".93 ± 0".80 . 



The m. e. again is too small as il does not contain the effect of the uncertainty 

 of the correction ,. 



