Arcot threw on the mighty power units that drove the ship, bracing
them against the pull of the beam.

"Wade! Use the molecular ray! Stop that beam!" Arcot ordered.

The ship was stationary, quivering under the titanic forces that
struggled for it. The enemy fleet raced toward them, trying to come to
the aid of the men in the tower.

The pale glow of the molecular beam reached out its ghostly finger and
touched the heavy-walled ray projector building. There was a sudden
flash of discharging energy, and the tower was hurled high in the air,
leaving only a gaping hole in the ground.

Instantly, with the collapse of the beam that held it, the _Ancient
Mariner_ shot backward, away from the scene of the battle. Arcot snapped
off the drive and turned on the invisibility apparatus. They hung
motionless, silent and invisible in the air, awaiting developments.

In close formation, one group of ships blocked the opening in the wall
of rays that the removal of one projector building had caused. Three
other ships went to investigate the wreck of the building that had
fallen a mile away.

The rest of the fleet circled the city, darting around, searching
frantically for the invisible enemy, fully aware of the danger of
collision. The unnerving tension of expecting it every second made them
erratic and nervous to the _n_th degree.

"They're sticking pretty close to home," said Arcot. "They don't seem to
be too anxious to play with us."

"They don't, do they?" Morey said, looking angry. "They might at least
have been willing to see what we wanted. I want to investigate some
other cities. Come on!" He had thoroughly enjoyed the rest at the little
mountain lake, and he was disappointed that they had been driven away.
Had they wanted to, he knew, they could easily have torn the entire city
out by the roots!

"I think we ought to smash them thoroughly," said Wade. "They're
certainly inhospitable people!"

"And I, for one, would like to know what that attraction ray was," said
Fuller curiously.

"The ray is easily understood after you take a look at the wreck it
made of some of these instruments," Arcot told him. "It was projected
magnetism. I can see how it might be done if you worked on it for a
while. The ray simply attracted everything in its path that was
magnetic, which included our lux metal hull.

"Luckily, most of our apparatus is shielded against magnetism. The few
things that aren't can be repaired easily. But I'll