. Mountains of
great height have been observed on the surface of this planet,
particularly in its lower or southern hemisphere. One has been
calculated at 10 3-4 miles in height, being about eight times higher,
in proportion to the bulk of the planet, than the loftiest mountains
upon earth. The matter of Mercury is of much greater density than that
of the earth, equalling lead in weight; so that a human being placed
upon its surface would be so strongly drawn towards the ground as
scarcely to be able to crawl.

Venus is a globe of about 7800 miles in diameter, or nearly the size
of the earth, rotating on its axis in 23 hours, 21 minutes, and 19
seconds, and revolving round the sun, at the distance of 68,000,000 of
miles in 225 days.--Like Mercury, it is visible to an observer on the
earth only in the morning and evening, but for a greater space of time
before sunrise and after sunset. It appears to us the most brilliant
and beautiful of all the planetary and stellar bodies, occasionally
giving so much light as to produce a sensible shadow. Observed through
a telescope, it appears horned, on account of our seeing only a part
of its luminous surface. The illuminating part of Venus occasionally
presents slight spots. It has been ascertained that its surface is
very unequal, the greatest mountains being in the southern hemisphere,
as in the case of both Mercury and the Earth. The higher mountains in
Venus range between 10 and 22 miles in altitude. The planet is also
enveloped in an atmosphere like that by which animal and vegetable
life is supported on earth; and it has consequently a twilight. Venus
performs its revolution round the sun in 225 days. Mercury and Venus
have been termed the Inferior Planets, as being placed within the
orbit of the Earth.

The Earth, the third planet in order, and one of the smaller size,
though not the smallest, is important to us, as the theatre on which
our race have been placed to 'live, move, and have their being.' It is
7902 miles in mean diameter, rotating on its axis in 24 hours, at a
mean distance of 95,000,000 of miles from the sun, round which it
revolves in 365 days, 5 hours, 50 minutes, and 57 seconds. As a planet
viewed from another of the planets, suppose the moon, 'It would
present a pretty, variegated, and sometimes a mottled appearance. The
distinction between its seas, oceans, continents, and islands, would
be clearly marked; they would appear like brighter and darker spot