Mr. Robertson on the Precession 
by the preceding article, the momentary nutation is 360 x 
x hbxy , radius being 1. 
Again, 2p : z : : T : ~~ — i. Also s/ 1 — xx = y, and, by 
the fluxional doctrine of circular arcs, z = ■■ ■ * ■ — ; and there- 
V 1 — xx 
fore t — — . These values of i andy being put for them 
2 pVi—xx 
in the above expression, the momentary nutation, or, which 
is the same thing, the fluxion of the nutation is 360 x ^ x 
Jjb x * 
Consequently the nutation, when the sun is at S, is 
it hbxx 
gb° x ^x 2 p 
When the sun arrives at the solstitial point C, then x be- 
comes equal to 1 , and the nutation is then 360 * x ^ = 
b . , ^ it c?—e % bx6o 
x — T— X 
r8 ox^x±? 
X J in degrees, or 10800 x +T „ „ p 
in seconds. Now t = one sidereal day, T = 3 66 £ = l -~-, and 
therefore 4T = 1 465. According to Sir Isaac Newton’s 
.determination of the figure of the earth, a is as 231, e as 230, 
and therefore 
461 
a% — - 6l * Also supposing the obliquity of 
the ecliptic 23 0 27' 45", =.3981487, and p = 3. 14159265. 
Consequently 10800 = x — - = 10800 x x 
x 2 l'^ - f - y 6 - 5 , the computation of which may be finished in the 
following manner. 
10800 Log. 4.0334238 
3 Log. 0.4771213 
461 Log. 2.6637009 
23.888922 Log. 1.3781998 
8-5524458 
8.3902115 
1465 Log. - - 3.1638376 
53361 Log. - - 4.7272240 
3.14159265 Log. 0.4971499 
8.3902115 
o. 1622343 = Log. of 1" 4529, and there* 
