386 W. Harkness—The Solar Parallazx. 
1856, LeVerrier nee talipp.2 MA) ci. corsa e2el. Dies 9°23 
1869. E. J. Stone (M S. vol. SUE GCAO ue Ses. 9°134 
1872, Nyrén (Mem. 70 Se. St. Petersbourg, 7° sér. t. xix, 
INO luce Need. 2. os ewes, ed eeu Ta ey 9°236 
With ¥=50"378, formula (19) gives the mass of the moon 
sc acai to three different values of the nutation constant 
as follows 
= 9”"°230 | 
ee 80°96 
1 
O= 9223 M=——— 
a ‘15 
= 9"°134 M= = —— 
ase se 65 
The change in the moon’s mass produced by a small change 
in the constant of nutation is given by the expression — 
a(x) = — 28:1d0 (21) 
In view - the fact that Peters attributed a probable error of 
+ 0’0154 to his most careful determination of the nutation 
constant, wud in view of the subsequent widely differing de- 
termination by E. J. Stone, it can scarcely be areas that 
the true vale of the nutation is known w thin oi This 
corresponds ai an uncertainty of +058 in the eaiebis of 
the moon’s m 
The lanai pe the sidereal month is 2,360,591°8 seconds of 
mean solar time. Assuming the observed value of the con- 
stant of lunar parallax: to be 8422” ‘7, Plana’s theory gives 
8419’’-62, and Delaunay’s theory 3419/59, for the value of P,.. 
I adopt '3419’-6, Substituting these values in formula (20), 
and the change in 
1 
81°77’ 
the mass produced by a small change in the adopted parallax 
is given by the expression 
a(x) = 5°925 dP (22) 
the resulting mass of the moon is 
The value of the lunar parallax now generay adopted, de- 
ends upon the investigations of Messrs. Breen and E. J. 
Bron ne. The results of these two gentlemen agree within 
0-01. The probable error of Mr. Breen’s result is not stated, 
while that of Mr. Stone’s is + 0/049. Nevertheless, it is not 
unlikely that the parallax: may be one or two-tenths of a sec- 
ond in error. An error of 0’:1 would produce an error of 
0°59 in the reciprocal of the mass. 
apie 
