1308 
mination of J, is a periodic term in the latitude, whose period is 
one month and whose coefficient is, by Brown’s theory : *) 
B = — [3.7046] J — 0".017. 
From the observations Brown finds’) 
B=— 8",19-+.0".06,— [0.40 + .0".20] . 7, 
where 7’ is the time expressed in centuries and counted from 1850.0. 
If we take the mean epoch of the observations, i.e. about 1875, 
we find’) J =0.001633, and consequently 
ea). == 207 SE Bette a ee 
It appears to me that this determination is not very reliable, 
chiefly on account of the large and uncertain coefficient of 7’ in 
the observed value. Brown proposes to use it not to determine «, 
but the inclination of the ecliptic and its secular variation. It seems 
very doubtful whether a correction to these elements thus determined 
would be a real improvement to our knowledge of them derived 
from other sources. 
A great weight is attributed by Brown to the determination of / 
from the motion of the perigee and the node. He finds 
et = 296.5 TE Oni ee el eae NN 
In deriving the m.e. no account has been taken of the uncertainty 
of the theoretically determined part of these motions due to other 
causes. Among these other causes, however, is the figure of the moon, 
which is very imperfectly known. It will be shown in the following 
paper that it is very well possible to adopt such values for the 
quantities defining this figure, that the motions of the perigee and 
the node are in agreement with the value et = 296.0. Smaller 
values of « however lead to very improbable conclusions regarding 
the constitution of the moon. 
All our discussions thus lead to the conclusion that none of the 
other determinations is equal in accuracy to, or can throw a doubt 
on the determination from the constant of precession. We must 
therefore adopt as final value of the compression the result of this 
determination, viz: 
Ee = 295.96 + 0.20. 
& 
1) Part V, Chapter XIII. (Memoirs of the R.A.S, Vol. LIX, Part I). On p. 80 
the inequality is given as — 8”.355 sin (w,-+ #). This should be — 8”.553. 
2) Monthly Notices, Vol. LX XIV, p. 564. Brown gives probable errors, which 
I have changed to mean errors. 
3) The theoretical value for 1875, corresponding to <—! = 297.0 is — 8”.312, 
the observed value is — 8/28, The difference is therefore 0 —C=-++0".03 and 
not —0”,03 as stated by Brown, l.c. p. 565, 
