212 PROCEEDINGS OF THE AMERICAN ACADEMY 



Peters, Numerus constans Nutationis, p. (195). 

 For 1800 -|- t 



m = 46."0623 + 0".0002849 t 

 n =20 .0607 — .0000863 t 



The formulae for secular variation are, as given by Menten, — 

 100 ^"2 = ^ -j- ^ tan 5 + (7 tan d^ 



100 '^^ = A' -\- B tan 8 



in which, employing Bessel's constants for 1860, — 



A = o!o0206 -f 0.00650 sin 2 a = o'.0O206 + i C 

 B= [8.4750] cos a + [6.811 «] sin a 



9 



(7= [8.1139] sin 2 « 



A' = — 0."0097 cos a — 0."4479 sin a 

 B = [9.2900 w] sin a\ 



