S. Newcomb—Mean Motion of the Moon. 405 
enon was actually seen. The, ee of the star — 
the moon’s limb is, in fact, a sudden nomenon which 
not require any measure of distance to Se well observed. 
VI. Observations of eclipses and occultations made by Heve- 
hus with a very imperfect clock regulated by altitudes taken 
with a quadrant with pinnules. It is well known that Hevelius 
would never use a telescope with ‘ta quadrant; so that the re- 
sults to be derived from the observations of this most’ indefati- 
gable observer do not correspond to the labor which he spent 
in making them. His observations are much better than those 
of Gassendus, but far more inaccurate than those made with the 
telescopic sig 
VII. Observations of Flamsteed at Greenwich, and of the 
astronomers of the French school, from 1672 to 1750. Flam- 
steed’s observations were published in the Historia Ccelestis. 
Those of the French — are not only for the most part 
unpublished, but seem to have ee totally forgotten — the 
time they were made aia I was fortunate enough to them 
in the archives of the Paris Dieaianan in 1871. Not oo 
it fears: wholly unreduced, but in many cases not even the 
of the occulted star was given. — reduction we ion 
eee ties tae been the most laborious part of my wor 
The observers have left no explanations wbaeeves of their mass 
of a and it was necessary to learn this by induction 
from the observations themselves; and from the calculations 
sectieses — and there through the ooks. 
supposed to commence. In the same class with these Paris 
observations are to be included those of ote at St. Peters- 
burgh, with which I was furnished by Str 
The following are some independent mean  corvedone 
by the observations of Bllialdas, grt Hevelius, Flam- 
steed, and the French astronom e list is incomplete, as 
the Maealation of the solar peters ia pe been finished; but 
it will suffice for the purposes of the present discussion :— 
1621 + 77" 1661 + 37” 
1630 +30 1666 24 oy 
1633 + 53 1680 + 30°4 
1635 +55 1682 + 255 
1639 + 23 1715 + 13°8 
1645 + 51 1725 + 7:0 
