ght junction of the crossover point.

"Here is where she lies now. Every 304.62 earth years, she completes
her orbit around the first sun, in this case Lauries, and passing the
equilibrium point between the two, begins to circle the second in the
opposite direction. There is a period of instability as she lies
between the pull of both; but nothing like this. Then slowly the pull
of the first sun grows less, she engages her second orbit, and
geological activity becomes more stable. All quite simple. There are
several examples of it just in the part of the galaxy we know."

"So how can a man change it?" came a voice.

"One man can't, obviously. But many men, with much planning and
outside help, can and have."

He expanded the graphic, receding the orbit and two suns to a lower
corner. Then tracing with the pointer a straight line away from the
planet's trajectory, he projected near the center of the screen a
miniature (but still too large for scale) image of the enemy station
that Percy had photographed in ultraviolet and sent back to them. This
he enlarged, until it filled all the screen.

Again expressions of dismay, and this time few kept silent. Its
already ominous outline distorted by the ultraviolet, it looked like
the huge, black and irregular hull of an ancient aircraft carrier, with
something like an enormous radar dish mounted securely to the
corrugated deck. As he rotated the image its high, central tower was
pointed directly at them.

"This is the cause of our troubles." He resolved the image with the
remote, turned it once more to show three similar but lesser tower
structures spread across the bottom, an irregular tripod.

"The concept of a gravity or 'tractor' beam is nothing new. It has
usually been used from ship to ship, or from static base to ship. Its
principals to date have either been magnetic, the creation of
artificial gravity, or kinetic, scrambling an object's own momentum to
bring it down. What we have here is the first case, a gravity beam,
though on a scale, and utilizing principles that are altogether new.
The towers at the bottom of the structure are pointed at neighboring
bodies, and serve only to hold the station in place. The central
tower, the one doing all the damage, is pointed directly at
Marcum-Lauries. That is why she won't engage her second orbit. That's
why internal pressures are ready to blow her apart. She is being
pulled by three sources at once, as we