eir immobility was
explained a moment later by an electric blue spark from something in
the shadow of their bodies.

Instantly Sime, who was at the controls, threw her hard-a-port, dived,
looped up. The first explosion of the tiny projectile tossed them up
like a monstrous wave, allowed them to drop sickeningly. The exhaust
tubes poured out a dense haze as Sime sought for distance. But they
were following him. He was five miles away when they finally got the
range. The vessel was jarred as if it had hit a rock. One of the
atomic pellets had exploded within a few feet of it. There was a
dismaying lurch. Sime picked himself up from the floor and dashed to
the controls.

"Everything's all right!" he shouted excitedly.

Tolto, however, was listening anxiously. There was a sharp crackling
at the stern, where, in a narrow space, the reaction motors provided
the forward motive power. In moments of excitement he referred to
himself in the third person. He did so now.

"Tolto's afraid that something's wrong! Smells hot, too!"

"Here, take the wheel!" Sime ordered. The explosions of the shells
were becoming less dangerous; they were getting too far away.

* * * * *

Sime burned his hand opening the narrow door. The paint was already
blistering off it. The trouble was immediately apparent. One of the
integrator chambers, in which atomic hydrogen was integrated to form
atomic iron and calcium (sometimes called the Michelson effect), had
sprung a leak. The heat escaping into the little room was not the
comparatively negligible heat of burning hydrogen, but the cosmic
energy of matter in creation. Sime slammed the door. The radiated
light was so intense that it stung even his hardened skin.

Looking through the rear range-finding periscope, he saw that they
were about twenty miles from the fort. They had ceased firing.

"Won't be long, Tolto," he said, taking over the controls himself
again, "before our tail's going to drop off. Got to make time."

It was, in fact, about ten minutes when, without warning, their nose
dropped.

"Tail's gone!" Sime announced.

Their momentum, under the destructive rate of speed they had been
making, was great, and as the levitators, with independent power
supply, still held them up, Sime continued to steer a course for the
twin cities of Tarog. He was aided by a light breeze, and the Sun was
nearing the western horizon by the time their rate of motion had
b