s through phases like those of the Moon, though we
cannot see them with the naked eye. To Venus also owe we mainly the
power of determining the distance, and consequently the magnitude, of
the Sun.

THE EARTH

Our own Earth has formed the subject of previous chapters. I will now,
therefore, only call attention to her movements, in which, of course,
though unconsciously, we participate. In the first place, the Earth
revolves on her axis in 24 hours. Her circumference at the tropics is
24,000 miles. Hence a person at the tropics is moving in this respect at
the rate of 1000 miles an hour, or over 16 miles a minute.

But more than this, astronomers have ascertained that the whole solar
system is engaged in a great voyage through space, moving towards a
point on the constellation of Hercules at the rate of at least 20,000
miles an hour, or over 300 miles a minute.[68]

But even more again, we revolve annually round the Sun in a mighty orbit
580,000,000 miles in circumference. In this respect we are moving at the
rate of no less than 60,000 miles an hour, or 1000 miles a minute--a
rate far exceeding of course, in fact by some 100 times, that of a
cannon ball.

How few of us know, how little we any of us realise, that we are rushing
through space with such enormous velocity.

MARS

To the naked eye Mars appears like a ruddy star of the first magnitude.
It has two satellites, which have been happily named Phobos and
Deimos--Fear and Dismay. It is little more than half as large as the
Earth, and, though generally far more distant, it sometimes approaches
us within 35,000,000 miles. This has enabled us to study its physical
structure. It seems very probable that there is water in Mars, and the
two poles are tipped with white, as if capped by ice and snow. It
presents also a series of remarkable parallel lines, the true nature of
which is not yet understood.

THE MINOR PLANETS

A glance at Figs. 51 and 52 will show that the distances of the Planets
from the Sun follow a certain rule.

If we take the numbers 0, 3, 6, 12, 24, 48, 96, each one (after the
second) the double of that preceding, and add four, we have the series.

4 7 10 16 28 52 100

Now the distances of the Planets from the Sun are as follow:--

Mercury. Venus. Earth. Mars. Jupiter. Saturn.
3.9 7.2 10 15.2 52.9 95.4

For this sequence, which was first noticed by Bode, and is known as
Bode's law,