the elements it has been
found necessary to confront with each other in order to arrive at
results expressed with such extreme precision? On the one hand,
mathematical formulae deduced from the principle of universal
gravitation; on the other, certain irregularities observed in the
returns of the moon to the meridian. An observing geometer, who from his
infancy had never quitted his study, and who had never viewed the
heavens except through a narrow aperture directed north and south,--to
whom nothing had ever been revealed respecting the bodies revolving
above his head, except that they attract each other according to the
Newtonian law of gravitation,--would still perceive that his narrow
abode was situated upon the surface of a spheroidal body, whose
equatorial axis was greater than its polar by a three hundred and sixth
part. In his isolated, fixed position he could still deduce his true
distance from the sun!

Laplace's improvement of the lunar tables not only promoted maritime
intercourse between distant countries, but preserved the lives of
mariners. Thanks to an unparalleled sagacity, to a limitless
perseverance, to an ever youthful and communicable ardor, Laplace solved
the celebrated problem of the longitude with a precision even greater
than the utmost needs of the art of navigation demanded. The ship, the
sport of the winds and tempests, no longer fears to lose its way in the
immensity of the ocean. In every place and at every time the pilot reads
in the starry heavens his distance from the meridian of Paris. The
extreme perfection of these tables of the moon places Laplace in the
ranks of the world's benefactors.

In the beginning of the year 1611, Galileo supposed that he found in the
eclipses of Jupiter's satellites a simple and rigorous solution of the
famous problem of the longitude, and attempts to introduce the new
method on board the numerous vessels of Spain and Holland at once began.
They failed because the necessary observations required powerful
telescopes, which could not be employed on a tossing ship. Even the
expectations of the serviceability of Galileo's methods for land
calculations proved premature. The movements of the satellites of
Jupiter are far less simple than the immortal Italian supposed them to
be. The labors of three more generations of astronomers and
mathematicians were needed to determine them, and the mathematical
genius of Laplace was needed to complete their labors. At the