- 406 S. Newcomb—Mean Motion of the Moon. 
The investigation is terminated at the epoch of 1750 so far 
as the reduction of observations is concerned, because there is 
reason to believe that a s tables are not greatly in error 
from 1750 to 1865. We may, therefore, in this preliminary 
discussion consider the tabular Sie zero between these epochs. 
For the epoch 1875 the correction given by some good observa- 
tions of occultations is —8’’0, a result 1” * less than that indi- 
cated by the observations at Greenwich and Washington. This 
discrepancy is quite surprising. It is, however, worthy of re- 
mark that Captain Tupman from a discussion of all the meridian 
observations made in Europe about the time in question ob- 
tained a mean result somewhat less than that given by Green- 
wich and Washington alone. It is well known ss Hansen’s 
term depending on eight times the mean motion of Venus mi- 
nus thirteen times that of the earth is almost enti rely empirical, 
being adjusted so as to satisfy the observations between 1750 
and 1 And since this term fails to satisfy the observations 
oakids of these limits, in fact making the tables worse than 
they would be without it, it ought to be rejected from the com- 
parison of theory with observation, Its effect upon the ancient 
results is, however, so small in comparison with the necessary 
error of the observations that its effect need not be taken into 
account. 
From the individual corrections to the moon’s mean longi- 
(1) (2) (3) (4) (5) 
- Hansen. H’; $=8""8. s—6"'18. At. 
—687 11" es by +16’ +397 —Tom 
381 —— GT ao aay +10 i 38 
—189 —20 20 4 +10 pees 14 
+134 —-16 —16 8 +4 — 6 
846 — 44 aie | fe | — 03 0 
$26" ee | + 03 -. 31 mn 
986 — 49 — 48 — 3°8 = 13 + 2 
1625 +650" +33" 7 age +128 
1660... +39 +18 SO i: Beene ee +3 
1675 +32 +15 ay 8-6 +34 
¥ +21 +16 ee —13 °5 +25 
1725 + 7 +16 - 68 86 +16 
1750 0 +19 +64 0-0 0 
1775 0 +31 +12 °5 + 8-4 —15 
1800 0 +15 +112 +1 + 9°5 —17 
1825 0 +32 +30 +44 — 8 
1850 0 ~=—4} — 46 0-0 0 
1875 — 8 —28 —15°8 —1°6 +14 
