240 Intelligence and Miscellaneous Articles. 
period depending on the action of the planet Venus, which Professor 
Hansen has proposed to introduce into the expressions for the 
moon’s motions. According to M. Delaunay’s calculations (the accu- - 
racy of which I have at present no intention of disputing) the value of 
the coefficient of the first of these disturbances—that, namely, whose 
period is about 273 years—is nearly the same as that attributed to it 
by the astronomer of Gotha; but the coefficient of the second, whose 
period is about 240 years (and which is the most important of the 
two, since its coefficient, calculated at first by Professor Hansen at 
23''-2, is according to his account at least 21'47), ought to be con- 
sidered, according to the researches of M. Delaunay, as altogether 
insensible, if not absolutely nothing. 
This conclusion, which is moreover perfectly in accordance with 
the announcement of the illustrious geometrician Poisson, published 
more than twenty-seven years ago in his memoir of 1833, gives rise 
to several questions of extreme importance, not only, as it seems to 
me, with respect to the perfection of the lunar tables, but also on the 
subject of scientific priority, and even of national honour. In order 
that the members of the Academy may be able to judge of this for 
themselves, it will be sufficient to mention that the principal cor- 
rections which the astronomers of the Greenwich Observatory have 
thought it necessary to make in the precious tables of our fellow- 
countryman Damoiseau—iables which are so remarkable from the 
fact that they are the first that were constructed from theory alone, 
without recourse to observation,—and the preference which they have 
accorded to the new lunar tables of Professor Hansen, are principally 
founded on the existence (considered by them to he conclusively 
demonstrated) of the two inequalities arising from the action of 
Venus, which M. Delaunay has just calculated. To this it will be 
sufficient to add that it was on these grounds that the extraordinary 
prize of £1000 was allotted to the same Professor by the Lords of 
the Admiralty, at the suggestion of the learned director of the Green- 
wich Observatory, for the really marvellous addition, as Mr. Airy 
calls it, which he has made to the lunar theory. This assertion, if 
suffered to pass without refutation, might lead us to undervalue the 
labours of those astronomers, French and foreign, who have 
brought about the rapid progress of this difficult theory, and have 
advanced it to its present state of perfection. 
I shall not now dwell further on these observations, which from their 
length would extend beyond the limits prescribed by the Academy 
to its own members, and still more to strangers whose claims it admits 
to the honour of an insertion in the Comptes Rendus ; but I thought 
it advisable to lose no time in announcing that Iam busily occupied 
in drawing up a memoir, in which all the observations called for by 
a question of gravity so great that the history of science has rarely 
furnished one similar to it will be detailed at length, so that it may 
not be supposed, either in France or abroad, that a memoir so im- 
portant as that of M: Delaunay has escaped unnoticed or remained 
unanswered.—Comptes Rendus, December 1860. 
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