164 SS. Newcomb— Variability of the Harth’s axial rotation. 
could find in astronomical literature, have been reduced to 
a homogeneous form, that is, they were corrected for the influ- 
ence of the different ane of chines glasses, for the in- 
fluence of Jupiter's different zenith-distances at the time of 
observation, for the influence of different distances of J ni: 
from the earth, and for the influence of all other circumstance 
which may change the apparent brightness of the satellite, pie 
which can be taken into consideration. Each observation gives 
an pene of condition of the form: 
t+a.y+p.2+(C—O)=0, (2) 
where z is the prong of the ecliptic tables, 4 the distance of 
Jupiter from the earth, y the correction of the adopted veloc- 
ity of light (493°-2 ay Delambre), ahd p.z a correction to be 
applied to the observations for different distances of the satel- 
lite from the center of Jupiter. The member p.z must be intro- 
duced in the equation of condition, because all the reductions 
of the observations are made by Bailly’s formula * (plus a con- 
stant member C), which is probably imperfect. 
“The solution of the equations (2) gives: 
a. Eclipse disappearing. b. Eclipse reappearing. 
#,—=—60°°6+8°'0 ¢,==— 9°0-+8°°0 
Y= +10°5241°74 Y j= —1°47E1°26 (3) 
2) —1°974:3°54 Z,=+1°6042°56 
VYort9*'89 Y,=+9°09 
(vy, and y, are the probable errors of an observation whose 
sight is unity.) 
“Then the same observations were corrected by the quan- 
(1) represent better the observations of the eclipses. 
‘Hach corrected observation gives us an equation of condi- 
tion of the same form as ( 
aaytp. 2+(C— O )=0, (4) 
in eeney only the last member O, raat another signification, 
because the observed times of the eclipses are ali correcte 
hae cat the table (1). The solution of these equations give 
the following results : 
a. Eclipse disappearing. 6. Eclipse reappearing. 
a’ >= — 42" 3+7°9 =o “7+6°°0 
y "pe +6'83841°72 y — anh 24 (5) 
2’ == —0°64+4:3°50 2’, +1°8242°52 
iy peel VY =+8 Ag 
“Tf you compare the ong of the probable errors Yo, ¥1 
¥'oo ¥' 19D cases, you will see that by means of the correc- 
* Histoire de l’Académie, Paris, MpccLxxI, p. 580. 
