er planets. It travels round the Sun in
224.7 days, at a mean distance of 67,000,000 miles, and with an average
velocity of 80,000 miles an hour. Its period of rotation is unknown. By
the observation of dusky spots on its surface, it has been surmised that
the planet completes a revolution on its axis in 23-1/4 hours; but other
observers doubt this and are inclined to believe that it always presents
the same face to the Sun. When at inferior conjunction Venus approaches
nearer to the Earth than any other planet, its distance then being
27,000,000 miles. Its greatest elongation varies from 45 deg. to 47 deg. 12'; it
therefore can never be much more than three hours above the horizon
before sunrise, or after sunset. Venus is a morning star when passing
from inferior to superior conjunction, and during the other half of its
synodical period it is an evening star. The planet attains its greatest
brilliancy at an elongation 40 deg. west or east of the Sun--five weeks
before and after inferior conjunction. It is at these periods, when at
its greatest brilliancy, that it casts a shadow at night.

Though so pleasing an object to the unaided eye, Venus, when observed
with the telescope, is often a source of disappointment--this is on
account of its dazzling brilliancy, which renders any accurate
definition of its surface impossible. Sir John Herschel writes: 'The
intense lustre of its illuminated part dazzles the sight, and
exaggerates every imperfection of the telescope; yet we see clearly that
its surface is not mottled over with permanent spots like the Moon; we
notice in it neither mountains nor shadows, but a uniform brightness, in
which sometimes we may indeed fancy, or perhaps more than fancy,
brighter or obscurer portions, but can seldom or never rest fully
satisfied of the fact.' It is believed that the surface of the planet is
invisible on account of the existence of a cloud-laden atmosphere by
which it is enveloped, and which may serve as a protection against the
intense glare of the sunshine and heat poured down by the not
far-distant Sun. Schroeter, a German astronomer, believed that he saw
lofty mountains on the surface of the planet, but their existence has
not been confirmed by any other observer. The Sun if viewed from Venus
would have a diameter nearly half as large again as when seen from the
Earth; it is therefore probable that the planet is subjected to a much
higher temperature than what is experienced on ou