492 
MR. G. H. DARWIN ON THE PRECESSION OF A VISCOUS SPHEROID. 
computation as originally carried out 4 ' was based on a method slightly different 
from that above explained, but I was able to adapt the old computation to the 
above method by the omission of certain terms and the application of certain 
correcting factors. For this reason the results in the first three tables are only given 
in round numbers. In the fourth table the length of day is given to the nearest 
five minutes, and the obliquity to the nearest five minutes of arc. 
The integration begins when the length of the sidereal day is 23 hrs. 56 min., 
the moon’s sidereal period 27'32l7 m. s. days, the obliquity of the ecliptic 23° 28', 
and the time zero. 
First period .—Integration from £= 1 to ‘88; seven equidistant values computed 
for finding the time, and four for the obliquity. 
For the obliquity the integration was not carried out exactly as above explained, in 
as far as that ~ log 10 tan i was found instead of y- l°gi 0 tail {(1 — A sin 2 7), but the differ¬ 
ence in method is very unimportant. The result marked* in Table III. is -j log 10 tan i. 
o ' ^ 
The estimated average value of i was 22° 15'. 
O 
The final result is 
i\ r =l"550, 7=20° 42', —* = 46,301,000 
Second period .—Integration from d= 1. to ’76 ; seven values computed for the tune, 
and four for the obliquity. 
The estimated average for 7 was 19°. 
The final result 
iV=l’559, 7=17° 21', —* = 10,275,000 
Third period .—Integration from d= I to "76 ; four values computed. 
The estimated average for i was 16° 30'. 
The final result 
A r =l"267, 7=15° 30', —*=326,000 
Fourth period .—Integration from 'c— 1 to "76 ; four values computed. 
The estimated average for i was 15°. The small terms in /3 and y were omitted in 
the equation of conservation of moment of momentum. All the solar and combined 
terms, except that in V in the equation of obliquity, were omitted. 
The final result 
IV=1T60, 7=14° 25', -*=10,300 
* I Pave to thank Mr. E. M. Langlet, of Trinity College, for carrying out the laborious computations. 
The work was checked throughout by myself. 
