"Oh dear, no," exclaimed the astronomer, smiling incredulously. "The
idea of signalling has got into people's heads through the outcry raised
about it some time ago, when Mars was in 'opposition' and near the
earth. I suppose you are thinking of the plan for raising and lowering
the lights of London to attract the notice of the Martians?"

"No; I believe I told you of the singular experience I had some five or
six years ago with an old astronomer, who thought he had established an
optical telegraph to Mars?"

"Oh, yes, I remember now. Ah, that poor old chap was insane. Like the
astronomer in _Rasselas_, he had brooded so long in solitude over his
visionary idea that he had come to imagine it a reality."

"Might there not be some truth in his notion? Perhaps he was only a
little before his time."

Gazen shook his head.

"You see," he replied, "Mars is a much older planet than ours. In winter
the Arctic snows extend to within forty degrees of the equator, and the
climate must be very cold. If human beings ever existed on it they must
have died out long ago, or sunk to the condition of the Eskimo."

"May not the climate be softened by conditions of land and sea unknown
to us? May not the science and civilisation of the Martians enable them
to cope with the low temperature?"

"The atmosphere of Mars is as rare as ours at a height of six miles, and