til the fifth time, and Aten turned with a
grimace of disappointment. Tommy's second shot burst in a freight
compartment and a man screamed. His voice carried horribly in the
silence of these heights. But Tommy shot again, and, again, and there
was a satisfying blue flash as a fifth big ship went fluttering
helplessly down.

Aten began to circle for height Tommy refilled the magazine.

"I'm bringing 'em down," he explained unnecessarily to Evelyn, "by
smashing their propellers. They have to land, and when they land
they're hostages--I hope!"

Confusion became apparent among the hostile planes. The one Yugna ship
was identified as the source of disaster. Tommy worked his rifle in
cold fury. He aimed at no man, but the propelling grids were large.
For a one-man ship they were five feet in diameter, and for the big
freight ships, they were circles fifteen feet across. They were
perfect targets, and Aten seemed to grasp the necessary tactics almost
instantly. Dead ahead or from straight astern, Tommy could not miss a
shot. The fleet of Rahn went fluttering downward. Fifteen of the
biggest were down, and six of the two-man planes. A sixteenth and
seventeenth flashed at their bows and drifted helplessly....

* * * * *

Then the one-man ships attacked. Six of them at once. Aten grinned and
dived for all of them. One by one, Tommy smashed their crystal grids
and watched them sinking unsteadily toward the towers of the city. As
his own ship drove over them, little golden flashes licked out.
Electric-charge weapons. One flash struck the wingtip of their plane,
and flame burst out, but Aten flung the ship into a mad whirl in which
the blaze was blown out.

Another freight ship helpless--and another. Then the air fleet of Rahn
turned and fled. The ornithopters winged away in heavy, creaking
terror. The others dived for speed and flattened out hardly above the
tree-fern jungle. They streaked away in ignominious panic. Aten darted
and circled above them and, as Tommy failed to fire, turned and went
racing back toward the city.

"After the first ones went down," observed Tommy, "they knew that if
they gassed the city we'd shoot them down into their own gas cloud. So
they ran away. I hope this gives us a pull."

The city's towers loomed before them. The lacy bridges swarmed with
human figures. Somewhere a fight was in progress about a grounded
plane from Rahn. Others seemed to have surrendered s