of Venus were several times as great as it actually is;
were this body, for instance, as large as Jupiter or some of the other
great planets, then its crescent could be readily discerned by the
unaided eye. It is curious to speculate on what might have been the
history of astronomy had Venus only been as large as Jupiter. Were
everyone able to see the crescent form without a telescope, it would
then have been an elementary and almost obvious truth that Venus must be
a dark body revolving round the sun. The analogy between Venus and our
earth would have been at once perceived; and the doctrine which was left
to be discovered by Copernicus in comparatively modern times might not
improbably have been handed down to us with the other discoveries which
have come from the ancient nations of the East.

[Illustration: Fig. 43. Venus, May 29th, 1889.]

Perhaps the most perfect drawing of Venus that has been hitherto
obtained is that made (Fig. 43) by Professor E.E. Barnard, on 29th May,
1889, with a 12-inch equatorial, at the Lick Observatory, which for this
purpose and on this occasion Professor Barnard found to be superior to
the 36-inch. The markings shown seem undoubtedly to exist on the planet,
and in 1897 Professor Barnard writes: "The circumstances under which
this drawing was made are memorable with me, for I never afterwards had
such perfect conditions to observe Venus."

In Fig. 44 we show three views of Venus under different aspects. The
planet is so much closer to the earth when the crescent is seen, that it
appears to be part of a much larger circle than that made by Venus when
more nearly full. This drawing shows the different aspects of the globe
in their true relative proportions. It is very difficult to perceive
distinctly any markings on the brilliantly lighted surface. Sometimes
observers have seen spots or other features, and occasionally the
pointed extremities of the horns have been irregular, as if to show that
the surface of Venus is not smooth. Some observers report having seen
white spots at the poles of Venus, in some degree resembling the more
conspicuous features of the same character to be seen on Mars.

[Illustration: Fig. 44.--Different Aspects of Venus in the Telescope.]

As it is so very difficult to see any markings on Venus, we are hardly
yet able to give a definite answer to the important question as to the
period of rotation of this planet round its axis. Various observers
during the las