,
as they watched the oncoming planet. "They didn't prove much--faded out
fast, but we think they established its length of day. Nobody knew how
many hours it took Venus to rotate on its axis. Some even thought it
always presented one face to the Sun as does Mercury. Others thought it
had a quick day, shorter than Earth's. Others gave it a day almost a
month long.

"Our prober rockets, carrying unmanned instruments, rather definitely
indicate that the planet has a day about twenty Earth-days long. Even
though it's shielded by the clouds, it must be miserably hot near the
surface."

"We'll soon find out." Burl grinned. "After Mercury, it couldn't be so
bad. Maybe it rains all the time."

Russ shrugged. "Who knows?" he said.

Venus was a vast sea of swirling white and gray clouds beneath them when
the _Magellan_ reached it. They hung above the cloud level, while
stretching below them lay the circular bowl of veiled mystery that was
the fabled evening star of poem and song.

Oberfield was probing the surface with the radiation counters for the
Sun-tap distortion. None had been detected from Earth, but observation
of the sunny face of Venus had always been difficult from the third
planetary orbit. But quickly the dour astronomer proved the fact. A
calculation of the planet's albedo--its rate of reflected
sunlight--showed that in one large central section there was a dimming
out. Somewhere in that spot, the light was being diverted.

Lockhart brought the _Magellan_ down gradually, closer, closer, and
finally sank it into the soupy atmosphere of Venus. Now, from every
viewplate, nothing reflected but a glare of white mist. But the ship was
not operating blind. Radar pierced the clouds, and from the wide screens
the crew could see that they had not yet touched the surface.

"Watch out for mountains," whispered Russ, hanging over Lockhart's
shoulder.

Their progress was slow but steady. The cloud bank around them did not
clear, but still glowed gray. After a descent of nearly two hours, there
was a flicker on the radar. It registered no features, no mountains,
nothing but a seemingly flat plain.

Above and around them the white clouds still blanketed everything. But
now Burl thought he saw a pale glow. Gradually the white faded away into
wisps and shreds, and in a flash the ship broke out of the clouds.

They hung beneath a grayish-white sky. Below them, scarcely a half mile
of visibility in misty, thin air, they s