As the days passed, the initial information was confirmed by new readings. The planet's atmosphere had a strong greenish tinge that was identified as chlorine. There was a great deal of oxygen in the stratosphere, and the comparison that everybody made was to a habitable Venus, but here masks would have to be worn against the irritating chlorine. Kesser and his assistants were uncertain about the exact composition of the hydrogen and nitrogen in the air below, but this merely increased their desire to go down and examine it.

At four thousand miles, the difference between water and land was sufficiently distinguishable for a photographic map to be made. Cameras, taking thousands of pictures a second, obtained a view entirely free of sparks.

There were four main continents, and uncountable islands. Fifty-nine hundred cities were large enough to show clearly, despite the distance. They were not lighted at night, but that could have been because there was no night in the Earth sense. When Alpha A was not shining down on the continents below, either Alpha B or Alpha C, or both, were shedding some equivalent of daylight.

'We mustn't assume,' said Captain Lesbee, in one of his daily talks on the intercoms, 'that the civilization here has not discovered electricity. Individual lights in houses would not necessarily be visible if they weren't used often.'

These talks, Lesbee discovered, did not serve the function that his father intended. There was a great deal of criticism, a feeling that the commander was becoming too cautious.

'Why don't we dive down,' said one man, 'collect some samples of the atmosphere, and end this uncertainty? If we can't breathe that stuff down there, let's find it out, and get started home.'

In spite of his confidence in his father, Lesbee found himself sharing the sentiment. Surely, the people below would not take violent offense. And, besides, if they departed immediately -