mpressed on it equal to that of the photosphere, a
movement in virtue of which it effected an entire revolution in
twenty-five days and a half. Laplace presented his conjectures on the
formation of the solar system with the diffidence inspired by a result
which was not founded upon calculation and observation.[39] Perhaps it
is to be regretted that they did not receive a more complete
development, especially in so far as concerns the division of the matter
into distinct rings; perhaps it would have been desirable if the
illustrious author had expressed himself more fully respecting the
primitive physical condition, the molecular condition of the nebula at
the expense of which the sun, planets, and satellites, of our system
were formed. It is perhaps especially to be regretted that Laplace
should have only briefly alluded to what he considered the obvious
possibility of movements of revolution having their origin in the action
of simple attractive forces, and to other questions of a similar nature.

Notwithstanding these defects, the ideas of the author of the _Mecanique
Celeste_ are still the only speculations of the kind which, by their
magnitude, their coherence, and their mathematical character, may be
justly considered as forming a physical cosmogony; those alone which in
the present day derive a powerful support from the results of the recent
researches of astronomers on the nebulae of every form and magnitude,
which are scattered throughout the celestial vault.

In this analysis, we have deemed it right to concentrate all our
attention upon the _Mecanique Celeste_. The _Systeme du Monde_ and the
_Theorie Analytique des Probabilites_ would also require detailed
notices.

The _Exposition du Systeme du Monde_ is the _Mecanique Celeste_ divested
of the great apparatus of analytical formulae which ought to be
attentively perused by every astronomer who, to use an expression of
Plato, is desirous of knowing the numbers which govern the physical
universe. It is in the _Exposition du Systeme du Monde_ that persons
unacquainted with mathematical studies will obtain an exact and
competent knowledge of the methods to which physical astronomy is
indebted for its astonishing progress. This work, written with a noble
simplicity of style, an exquisite propriety of expression, and a
scrupulous accuracy, is terminated by a sketch of the history of
astronomy, universally ranked in the present day among the finest
monuments of th