True, wherever they might be, a diffused molecular would find them and
destroy all life save under the few screens, but if the Thessians once
diffused their rays, without entering the atmosphere, the broken screen
would once more be able to hold.

No fleet had kept the Thessian forces out of this atmosphere, but dozens
of more adequately powered artificial matter bomb stations had taught
Thett respect for Talso. But Talso's own ray screen had stopped their
bombs. They could only send their bombs as high as the screen. They did
not have Arcot's tremendous control power to maintain the matter without
difficulty even beyond a screen.

At last the screen had fallen, and the Thessian ships, a hole once made,
were able to move, and kept that hole always under them, though if it
once were closed, they would again have the struggle to open it.

Exploding matter bombs had twice caused such spatial strains and ionized
conditions as to come near closing it, but finally the Thessian fleet
had arranged a ring of ships about the hole, and opened a cylinder of
rays that reached down to the planet.

Like some gigantic plow the rays tore up mountains, oceans, glaciers and
land. Tremendous chasms opened in straight lines as it plowed along.
Unprotected cities flashed into fountains of rock and soil and steel
that leaped upwards as the rays touched, and were gone. Protected
cities, their screens blazing briefly under the enormous ray
concentrations as the ships moved on, unheeding, stood safe on islands
of safety amidst the destruction. Here in the lower air, where ions
would be so plentiful, Thett did not try to break down the screens, for
the air would aid the defenders.

Finally, as Thett's forces had planned, they came to one of the ionized
layer ray-screen stations that was still projecting its cone of
protective screening to the layer above. Every available ray was turned
on that station, and, designed as it was for protecting part of a world,
the station was itself protected, but slowly, slowly as its already
heated tubes weakened their electronic emission, the disc of ions
retreated more and more toward the station, as, like some splashing
stream, the Thessian rays played upon it forcing it back. A rapidly
accelerating retreat, faster and faster, as the disc changed from the
dull red of normal defense to the higher and bluer quanta of failing,
less complete defense, the disc of interference retreated.

Then, with a flash