last of Mars Center sank in bubbling
lava. "They stung as they died." For some minutes he was silent.

"We must move on," he said at length. "I have been thinking, and it
seems best that a few ships land here, and establish a fort, while some
twenty move on to the satellite of the third planet and destroy the fort
there. We cannot operate against the planet while that hangs above us."

Seven ships settled to Mars, while the fleet came up from Jupiter to
join with Gresth Gkae's flight of ships on its way to Luna.

An automatically controlled ship was sent ahead, and began the
bombardment. It approached slowly, and was not destroyed by the UV beams
till it had come to within 40,000 miles of the fort. At 60,000 Gresth
Gkae stationed his fleet--and returned to 150,000 immediately as the
titanic UV beams of the Lunar Fort stretched out to their maximum range.
The focus made a difference. One ship started limping back to Jupiter,
in tow of a second, while the rest began the slow, methodical work of
wearing down the defenses of the Lunar Fort.

Kendall looked out at the magnificent display of clashing, warring
energies, the great, whirling spheres and discs of opalescent flame, and
turned away sadly. "The men at Deenmor must have watched that for days.
And at Mars Center."

"How long can we hold out?" asked McLaurin.

"Three weeks or so, at the present rate. That's a long time, really. And
we can escape if we want to. The UV beams here have a greater range than
any weapon the Strangers have, and with Earth so near--oh, we could
escape. Little good."

"What are you going to do?"

"I," said Buck Kendall, suddenly savage, "am going to consign all the
math machines in the universe to eternal damnation--and go ahead and
build a machine anyway. I _know_ that thing ought to be right. The
math's wrong."

"There is no other thing to try?"

"A billion others. I don't know how many others. We ought to get atomic
energy somehow. But that thing infuriates me. A hundred things that math
has predicted, that I have checked by experiment, simple little things.
But--when I carry it through to the point where I can get something
useful--it wriggles off into--uncertainty."

Kendall stalked off to the laboratory. Devin was there working over the
calculus machines, and Kendall called him angrily. Then more apologetic,
he explained it was anger at himself. "Devin, I'm going to make that
thing, if it blows up and kills me. I'm going to m