es asked
for more detailed plans. Smithers stood up to go with them.

"You're a hero, now, Smithers," Tommy informed him exultantly.
"They'll work you to death and call you blessed!"

"Yes, sir," said Smithers. "These fellas are right good mechanics.
They just happened to miss this trick." He paused. "Uh--where's Miss
Evelyn?"

"With Aten's--wife," said Tommy. This was no time to discuss the
marital system of Yugna. "We were prisoners until this morning. Now
we're guests of honor. Evelyn's talking to a lot of women and trying
to boost our prestige."

* * * * *

Smithers went over to the gesticulating group of draftsmen. He settled
down to explain by drawings, since he had not a word of their
language. In a few minutes a group went rushing away with the sketch
tablets held jealously to their breasts, bound for workshops. Other
men appeared to present new problems. A wave of sheer enthusiasm was
in being. A new idea which would lessen the demands of the machines
was a godsend to these folk.

Then Denham blew a smoke ring and said meditatively:

"I think I've got something too, Tommy. Ultra-sonic vibrations. Sound
waves at two to three hundred thousand per second. Air won't carry
them. Liquids will. They use 'em to sterilize milk, killing the germs
by sound waves carried through the fluid. I think we can start some
ultra-sonic generators out there that will go through the wet soil and
kill all vegetation within a given range. We might clear away the
jungle for half a mile or so and then use ultra-sonic beams to help it
clear while new food-plants are tried out."

Tommy's eyes glowed.

"You've given yourself a job! We'll turn this planet upside down."

"We'll have to," said Denham drily. "This city may believe in you, but
there are others, and these folk are a little too clever. There's no
reason why some other city shouldn't attack Earth, if they seriously
attack the problem of building a Tube."

Tommy ground his teeth, frowning. Then he started up. There was a new
noise down in the city. A sudden flare of intolerable illumination
broke out. There was an explosion, many screams, then the yelling
tumult of men in deadly battle.

* * * * *

Every man on the tower terrace was facing toward the noise, staring.
The white-bearded man gave an order, deliberately. Men rushed. But as
they swarmed toward an exit, a green beam of light appeared near the
u