place, which, properly used, would reduce not only just the room and
its contents to glowing slag, but take half the city with it. But he
had no idea which, or which combination, would do it.

And here Sssuri could be no help. The mermen had made great strides
forward in biological and mental sciences, but mechanics was a closed
section of learning because of their enforced habitat under the sea,
and of machines they knew less than the colonists.

"I have been thinking--" Sssuri broke into his companion's chain of
reasoning, "of what we may do. And perhaps there is a way to reach the
sea more swiftly than by returning overland."

"Downriver? But you said that way may have its watching devices."

"Which would be centered on objects coming upstream, not down. But in
this city there should be yet another way--"

He did not enlarge upon that, but since he apparently knew what he was
doing, Dalgard let him play guide once more. They recrossed the
sluggish river, the scout looking into its murky depths with little
relish for it as a means of transportation. Though it had an oily,
flowing current, there was a suggestion of stagnant water with
unpleasant surprises waiting beneath its turgid surface.

For the second time they entered the arena. Avoiding the bodies,
Sssuri made a circuit of the sanded floor. He did not turn in at the
archway which led to the storage place, but paused before another as
if there lay what he had been searching for.