Obliquity of the Ecliptic. 13 
sun’s declination for the 9th of November 173, at noon, at 
Loyang, which is 7° 20' 6” further east than Paris; and 
if we multiply afterwards by y the variation of declination. 
corresponding to 10’ of increase in the situation of the sun ; 
and, finally, 1f we design by z an increase in the obliquity 
of the ecliptic ;—we shall have the two equations, 
216° 56’ 58”,9—y- 2 53,1 —% 0,69421 = 38° 29’ 14,0 
X—15 37 44 ,3+y°3 5 ,9—x%'0,63720=39 31 Q 44 
which two equations give 
v= 55° 14’ 14.4 + 2 0,66668 ; a 
and therefore the latitude of Loyang resulting from these. 
observations is 34° 45’ 45”,6 — 22. 
By a mean between F.F. Regis and Mailla’s observations, 
this latitude is 34° 46’ 15: and_it has been seen that this 
resu.t-differs little from what is given by Tcheou-Kong’s. 
observations ; thus we have 
. 2 i$ OO Hs 
which gives x= — 44",1. The ecliptic’s obliquity: given 
by the quoted tables was at that period 13° 54” greater than 
in 1750. The preceding observations give therefore an 
increase of 13’ 9’,9 in that obliquity, differing very little 
from the result of the formulas of Méc. Cél. on which these’ 
tables are founded. In order to admit an invariable obli- 
quity,’x should be made = —13' 54”; in which case we 
should have'34° 55’ 1",6 for Loyang’s latitude, which can- 
not be admitted. 
: : . . . 
Supposing z=0 in the preceding equations, we shall have 
y= — 1,7242. 
- The preceding observations, therefore, appear to indicate 
a diminution of 17’ in the sun’s place, as indicated by the 
tables. This diminution is too considerable to be admissible, 
and it is morenatural to attributeit to errors in observations. 
Supposing y and z = 0, we shall have by the first observa- 
tion 34° 40’ 47" for the pole’s altitude, and 34° 51’ 6”,3 by> 
the second; which gives a mean of 34° 45’ 56”,7 for that 
altitude. 
In the year 461, Tsou-tchong, a learned Chinese astro- 
nomer, determined the instant of the winter solstice. This 
is what is related on that subject in the MS. quoted by 
Father Gaubil. (Conn. des Tems for 1809, p. 389.) 
‘¢ This solstice was determined at Nankin, the year Sin- 
’ tcheou, 5th of Tamin, on the day Y-yeou, 31 ke after mid- 
night; which answers to the year 461, 20th December, 
7* 26' 24” of the morning. 
“Phe 
