Retrospect of French Literature—Miscellanies. 651 
In this celebrated work, we not only 
learn what has been achieved by other 
famous men, such as Newton, Descartes, 
Clairaut, Euler, Mayer, Lagrange, Hal- 
ley, D’Alembert, &c. but the author has 
also communicated his own researches 
relative to the theory of the Moon, in 
which he confirms the principles laid 
down by our illustrious countryman, in 
the first edition of the Principia. He has 
also elucidated the periodical inequalities 
of Jupiter and Saturn, and extricated 
modern philosophy from the dilemma in- 
to which it had been thrown by some 
recent discoveries 
The phenomenon of the Tides, is a 
subject that has engaged the especial at- 
tention of the French astronomer, and 
the theory here given has heen strength- 
ened by observations made at the port of 
Brest, a place admirably calculated by 
nature for observations of this kind, We 
accordingly find: 
1. That there is an exact coincidence 
between the laws by which the Tides 
diminish from their maximum at the full 
and change of the Moon, to their mini- 
mun at the first and third quarters. 
2. It appears also, by actual experi- 
ment, that the heights of the Tides at 
their maximum near the equinox, is to 
their height (provided similar occurrences 
take place) at the sulstices, nearly as the 
square of the radius to the square of the 
co-sine of the declination of the Sun at 
the solstice. 
3, That the influence of the Moon on 
the Tides, increases as the cube of her 
parallax. 
4. That the retardation of the Tides, 
from one day to another, agrees equally 
well with both theory and practice. 
One of the most curious, as well as 
mest learned parts of the present work, 
is dedicated to an enquiry relative to the 
stability of the sea; and La Place is 
clearly of opinion, that the equilibrium 
has always been, and must necessarily be 
so preserved, as to render any of those 
changes, hinted at by some philosophers, 
impossible, at least so far as this may 
have been considered a primary cause. 
The precise figure of the earth, which 
Newton long since determined, engages 
the particular attention of the author, 
and the fifth book is devoted to the pre- 
cession of the equinoxes. D’Alembert 
was the first to solve this grand and in- 
teresting problem, by means of equations, 
and he has been followed by Simpson, and 
Walmsley, as well as by La Place, who has 
trodden the same ground again, although 
somewhat in a different track. The 
grand deductions, appear to be precisely 
the same, but others of an inferior, al- 
though interesting kind, are also intro- 
duced, It is proved that the phenomena 
of the procession and nutation, are and 
niust be precisely the same, as if the 
whole of our planet were one solid mass, 
while neither the curreuts in the sea, 
the rivers running into it, nor trade winds 
agitating its surface in a particular di- 
rection, can have any effect in alter- 
ing the earth’s rotation on its axis. So 
certain and regular is this law, that even 
earthquakes themselves cannot shake it, 
We learn also, that the density of the 
earth increases from the circumference 
towards the centre, that it is an elliptic 
spheroid, and that its compression at the 
poles, is between the limits of 74g and 
st_ part of the radius of the equator. 
The eighth book is dedicated to the 
secondary planets, particularly the sa- 
tellites of. Jupiter, which have astonished 
and puzzled many astronomers on ac- 
count of the quickness of their revolu- 
tions, during the comparatively short 
period in which they have been known 
to us. Bradley was one of the first to 
discover the periodical system of theip 
inequalities. 
In book IX, the very interesting subject 
of comets is treated of, and a place 
points out the methods of determining 
their orbits; and also the effects produced 
on them, when they come within the 
range of the attraction of any of the 
planets. It ison this occasion that he 
collects all his learning, and employs all 
his genius, to describe, calenlate, and 
demonstrate the laws by which these 
erratic bodies are governed. 
He also displays great skill and ree - 
search in the next book, particularly 
while treating of refraction. He ther 
tries to determine the angle of the ray of 
light, which in its progress from the sun, 
enters the earth’s atmosphere, and takes 
a new direction, through a denser me- 
dium, as it approaches towards the earth, 
The “Celestial Mechanism,” of La 
Place, has attained a high celebrity on 
the continent, and cannot fail to be read 
and admired in this country, by all those 
who are capable of relishing its merits, 
estimating the ingenuity of the author, 
or following him in his nice and difficult 
calculations. 
“* Archzographie,” &c.—Introduction 
to the Knowledge of the Monuments of 
Antiquity, by Jerome JacquesOBERLINy 
Professor of Philosophy ext sits (ie : 
vT 6 
