computer. He knew, without being able to explain how he knew, every mathematical fact and factor of the problem. Its solution was complete. He knew the exact point in space and the exact instant in time at which the calculated deceleration must begin; by the aid of the sweep second-hand of the chronometer—one full revolution of the dial every second—he was now setting the clicking mechanism so that it would announce that instant. His hand swayed back and forth—a finger snapped down—and the sharp-toned instrument began to give out its crisp, precisely-spaced clicks.

"Got it on the hair!" Cloud snapped. "Get ready, Thlaskin. Seconds! Four! Three! Two! One! Click!"

Exactly upon the click the cruiser's driving blasts smashed on. There was a cruelly wrenching shock as everything aboard acquired suddenly a more-than-three-times-Earthly weight.

The Dhilians merely twitched. The Tomigan, standing behind the pilot's seat, supporting and steadying his wounded head in its rest, settled almost imperceptibly, but her firmly gentle hands did not yield a millimeter. The nurse sank deeply into the cushioned bench upon which she was lying, her quick, bright eyes remaining fixed upon her patient. The Chickladorian girl, in her hammock, fainted quietly.

And downward the big ship hurtled, tail first, directly toward the now glowing screens of a fortress. Driving jets are not orthodox weapons. But properly applied, they can become efficient ones indeed, and these were being applied with micrometric exactitude.

Down—down—down! The frantic Uhalians thought that it was crashing—thought it a suicide ship. Nevertheless, they fought it. The threatened fortress and its neighbors hurled out their every beam; the Uhalian ships dived frantically at the invader and tried their best to blast her down.

In vain. The cruiser's screens carried the load effortlessly.

Down she drove. The fortress' screens flamed ever brighter, radiating ever higher under the terrific bombardment. Closer—hotter! Nor did the frightful blast waver appreciably; the Chickladorian was a master pilot. Down!

"Set up a plus ten, Thlaskin," Cloud ordered quietly. "I missed it a bit—air density and the beams. Give it to her on the third click from ... this!"

"Plus ten it is, sir—on!"

A bare hundred yards now, and the ship of space was still plunging earthward at terrific speed. The 

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