XXX Mr. Pickering’s Eulogy on 
result of the efforts of those disciples was, that, at the close of the 
last century, there was not one of the phenomena, which had per- 
plexed astronomers in the motions of the heavenly bodies, that 
could not be explained on the principle of gravitation; and the 
conclusions of theory were reconciled with the observations, except 
so far as imperfections in practice will ever occasion slight deviations 
from theory. 
The time, then, seemed to have come, as La Place himself had 
said of Newton, for some man of genius to reduce into one work 
the whole theory of astronomy, with all the discoveries in the 
science since the age of the great English geometer ; and La Place 
was the man, in all Europe, whom the scientific world would have 
selected for so great an undertaking.* 
This vast labor La Place undertook in his Mécanique Céleste. 
He says, in his brief but comprehensive Preface, “The whole of the 
results of gravitation, upon the equilibrium and motions of the fluid 
and solid bodies which compose the solar system and the similar 
systems existing in the immensity of space, constitute the object of 
Celestial Mechanics, or the application of the principles of me- 
chanics to the motions and figures of the heavenly bodies. Astron- 
omy, considered in the most general manner, is a great problem of 
mechanics, in which the elements of the motions are the arbitrary 
constant quantities. The solution of this problem depends, at the 
same time, upon the accuracy of the observations and the perfection 
of the analysis. It is very important to reject every empirical 
process, and to complete the analysis, so that it shall not be neces- 
sary to derive from observations any but indispensable data. The 
intention of this work is to obtain, as far as may be in my power, 
this interesting result.” 
* Edinburgh Review, Vol. II. p. 253. 
