"Or else what?" asked Dorothy.
"Just a hunch. I wouldn't wonder if——"
"Hold it, Dicky! Remember I had to put you to bed after that last hunch you had!"
"Here it is, anyway. Mart, what would be the logical line of evolution when the planet has become so old that all the land has been eroded to a level below that of the ocean? You picked us out an old one, all right—so old that there's no land left. Would a highly civilized people revert to fish? That seems like a backward move to me, but what other answer is possible?"
"Probably not to true fishes—although they might easily develop some fish-like traits. I do not believe, however, that they would go back to gills or to cold blood."
"What are you two saying?" interrupted Margaret. "Do you mean to say that you think fish live here instead of people, and that fish did all this?" as she waved her hand at the complicated machinery about them.
"Not fish exactly, no." Crane paused in thought. "Merely a people who have adjusted themselves to their environment through conscious or natural selection. We had a talk about this very thing in our first trip, shortly after I met you. Remember? I commented on the fact that there must be life throughout the Universe, much of it that we could not understand; and you replied that there would be no reason to suppose them awful because incomprehensible. That may be the case here."
"Well, I'm going to find out," declared Seaton, as he appeared with a box full of coils, tubes, and other apparatus.
"How?" asked Dorothy, curiously.
"Fix me up a detector and follow up one of those beams. Find its frequency and direction, first, you know, then pick it up outside and follow it to where it's going. It'll go through anything, of course, but I can trap off enough of it to follow it, even if it's tight enough to choke itself," said Seaton.