e are too apt to confound the precision of the laws of nature,
with the perfection of human theories. Man observes the phenomena of the
heavens, and derives his means of predicting what will be, from what has
been. Hence the motions of the heavenly bodies are known to within a
trifling amount of the truth; but it does not follow that the true
explanation is always given by theory. If this were so, the mass of the
moon (for instance) ought to be the same, whether deduced from the
principle of gravitation or from some other source. This is not so.
Newton found it 1/40 of that of the earth. La Place, from a profound
theoretical discussion of the tides, gave it as 1/58.6, while from other
sources he found a necessity of diminishing it still more, to 1/68, and
finally as low as 1/75. Bailly, Herschel, and others, from the nutation
of the earth's axis, only found 1/80, and the Baron Lindenau deduced the
mass from the same phenomenon 1/88. In a very recent work by Mr. Hind,
he uses this last value in certain computations, and remarks, that we
shall not be very far wrong in considering it as 1/80 of the mass of the
earth. This shows the uncertainty of the matter in 1852. If astronomy is
so perfect as to determine the parallax of a fixed star, which is almost
always less than one second, why is it that the mass of the moon is not
more nearly approximated? Every two weeks the sun's longitude is
affected by the position of the moon, alternately increasing and
diminishing it, by a quantity depending solely upon the relative mass of
the earth and moon, and is a gross quantity compared to the parallax of
a star. So, also, the horizontal parallax--the most palpable of all
methods--taken by different observers at Berlin, and the Cape of Good
Hope, (a very respectable base line, one would suppose,) makes the mass
of the moon greater than its value derived from nutation; the first
giving about 1/70, the last about 1/74.2. Does not this declare that it
is unsafe to depend too absolutely on the strict wording of the
Newtonian law of gravitation. Happily our theory furnishes us with the
correct value of the moon's mass, written legibly on the surface of the
earth; and it comes out nearly what these two phenomena always gave it,
viz.: 1/72.3 of that of the earth. In another place we shall inquire
into the cause of the discrepancy as given by the nutation of the earth.

MOTION OF THE AXIS OF THE VORTEX.

If the axis of the terral vortex doe