int, the _Skylark_ hopped over the
structure and down to the surface of the small central lagoon previously
noticed. Close to the water, it was seen that there was plenty of room
for the vessel to move about beneath the roof of reflectors, and that
the island was one solid stand of tide-motors. At one end of the lagoon
was an open metal structure, the only building visible, and Seaton
brought the space-cruiser up to it and through the huge opening--for
door there was none. The interior of the room was lighted by long,
tubular lights running around in front of the walls, which were
veritable switchboards. Row after row and tier upon tier stood the
instruments, plainly electrical meters of enormous capacity and equally
plainly in full operation, but no wiring or bus-bar could be seen.
Before each row of instruments there was a narrow walk, with steps
leading down into the water of the lagoon. Every part of the great room
was plainly visible, and not a living being was even watching that vast
instrument-board.

"What do you make of it, Dick?" asked Crane, slowly.

"No wiring--tight beam transmission. The Fenachrone do it with two
matched-frequency separable units. Millions and millions of kilowatts
there, if I'm any judge. Absolutely automatic too, or else----" Seaton's
voice died away.

"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 m