ll the fleet's column raced on.

* * * * *

At last the column slowed. Far ahead the merest bulge broke the level
line where sky and waters met. The amphibian city of the Ralas! At
Fellows' order-the flying-boats sank downward until they moved just
above the waters. Another order made the green hosts don the grotesque
helmets. Norman found that while cumbersome their oxygen supply was
unfailing. They shot on again at highest speed, but as the gigantic
black dome of the frog-city grew in their vision there darted up from
around it suddenly a far-flung swarm of black spots.

"Rala boats!"

The muffled exclamation was Fellows'. There needed now no order on his
part, though. Like hawks, leaping for prey, the fleet of the green men
sprang through the air. Norman, clutching the force-gun between his
knees, had time only to see that the Rala craft were a few hundred in
number and that, contemptuous of the greater odds that favored these
humans they had so long oppressed, they were flying straight to meet
them. Then the two fleets met--and were spinning side by side above
the waters.

Norman saw the thing only as a wild whirl of Rala boats toward and
beside them, great green frog-men crowding the craft, their force-guns
hailing shells. Automatically, with the old air-fighting instinct, his
fingers had pressed the catch of the gun between his knees and as its
shells flicked toward the rushing boats he saw areas of nothingness
opening suddenly in their mass, shells striking and exploding in
annihilating invisibility there and in their own fleet.

The two fleets mingled and merged momentarily, the battle becoming a
thing of madness, a huge whirl of black and glittering flying-boats
together, striking shells exploding nothingness about them. The Ralas
were fighting like demons.

The merged, terrific combat lasted but moments; could last but
moments. Norman, his gun's magazine empty, seemed to see the mass of
struggling ships splittering, diverging; then saw that the black craft
were dropping, plummeting downward toward the waves! The Ralas,
stunned by that minute of terrific combat, were fleeing. Muffled cries
and cheers came from about him as the glittering flying-boats of the
green men shot after them. They crashed down into the waters and
curved deeply into their green-depths, toward the gigantic dome.

* * * * *

Ahead the Rala boats were in flight toward