stations just beyond the range of the Mars Center Station. Naturally,
near so powerful a center, these stations had never been strong. They
fell rapidly. But they had been counted on by Mars Center as auxiliary
supports. McLaurin had sent very definite orders to Mars Center
forbidding any action on their part, save gathering of power-supplies.

At last the direct attack on Mars Center was launched. For the first
time, the Mirans saw one of the fifteen-foot beams. Mars' atmosphere is
thin, and there is little ozone. The ultra-violet beams were nearly as
effective as in empty space. When the Mirans dropped their ships, a full
thirty of them, into the circle formation, Mars Center answered at once.
All four beams started.

Those fifteen-foot beams, connected directly to huge atostor release
apparatus, delivered a maximum power of two and three-quarter billion
horsepower, each. The first Miran ship struck, sparkled magnificently,
and a terrific cascade of white-hot metal rolled down from its nose. The
great ship nosed down and to the left abruptly, accelerated swiftly--and
crashed with tremendous energy on the plain outside of Mars Center City.
White, unwavering flames licked up suddenly, and made a column five
hundred feet high against the dark sky. Then the wreck exploded with a
violence that left a crater half a mile across.

Three other ships had been struck, and were rapidly retreating. Another
try was made for the ring formation, and four more ships were wounded,
and replaced. The ring did not retreat, but the great magnetic field
started. Atomic and gamma ray bombs started now, flashing sometimes
dangerously close to the station as its magnetic field battled the
rotating field of the ships. The four greater beams, and many smaller
ones were in swift and angry action. Not more than a ten-second exposure
could be endured by any one ship, before it must retreat.

* * * * *

For five minutes the Mirans hung doggedly at their task. Then, wisely,
they retreated. Of the fleet, not more than seven ships remained
untouched. Mars Center Station had held--at what cost only they knew.
Five hundred tons of their mercury had been exhausted in that brief five
minutes. One hundred tons a minute had flowed into and out of the
atostor apparatus. Mars Center radioed for help, when the fleet lifted.

There was one other station on Mars that stood a good chance of
survival, Deenmor Station, with three