212 PROCEEDINGS OP THE AMERICAN ACADEMY 



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

 For 1800 + t 



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

 n = 20 .0G07 — .00008G3 t 



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

 100 ^^^ = A-\-Bian8-\-C tan 8- 



100 ^ = J' + j5' tan 8 

 in which, employing Bessel's constants for 18G0, — 



A = o!o020G + 0.00650 sin 2 a = o'.0020G + ^ C 

 B= [8.4750] cos « + [G.811 n^ sin a 

 C= [8.1130] sin 2 « 



A' = — 0."0097 cos a — 0."4479 sin « 

 B = [9.2900 w] sin a\ 



