diminution of density, from the one nearest to the sun to that which
is most distant. With respect to density alone, we find, taking
water as a measure and counting it as one, that Saturn is 13/32, or
less than half; Jupiter, 1 1/24; Mars, 3 2/7; Earth, 4 1/2; Venus, 5
11/15; Mercury 9 9/10, or about the weight of lead. Then the
distances are curiously relative. It has been found that if we place
the following line of numbers, -

0 3 6 12 24 48 96 192,

and add 4 to each, we shall have a series denoting the respective
distances of the planets from the sun. It will stand thus -

4 7 10 16 28 52 100 196
Merc. Venus. Earth. Mars. Jupiter. Saturn. Uranus.

It will be observed that the first row of figures goes on from the
second on the left hand in a succession of duplications, or
multiplications by 2. Surely there is here a most surprising proof
of the unity which I am claiming for the solar system. It was
remarked when this curious relation was first detected, that there
was a want of a planet corresponding to 28; the difficulty was
afterwards considered as in a great measure overcome, by the
discovery of four small planets revolving at nearly one mean distance
from the sun, between Mars and Jupiter. The distances bear an
equally interesting mathematical relation to the times of the
revolutions round the sun. It has been found that, with respect to
any two planets, the squares of the times of revolution are to each
other in the same proportion as the cubes of their mean distances,--a
most surprising result, for the discovery of which the world was