man did, the full truth of the remark.

He saw them as they struck the fire; saw the whirling blast of snow that drove under them as they went into the fight with the wildest enemy of man; and he knew that a smothering blanket of carbon dioxide was driving with hurricane force upon the flames.

H

On the instrument at his side flashed the "Ascend!" order of the squadron commander, and an instant later the flight reappeared a half mile away.

The commander must have sighted O'Rourke's ship. "Shall we repeat over same course?" the instrument spelled out, while Danny, circling above, watched the effects of the drive.

It had checked the flames, that first blast of the CO_2 squadron; he saw blackened, jagged trees where a roaring furnace had been. But the flames were building up again. "Repeat!" O'Rourke answered; then watched them drive in again.

From a wooded valley beyond a low range came a call for help. A lone ship in the red and black of the service had driven down into that valley that was like a cauldron of seething flame.

"I can't touch it!" a thin voice said. "The up-draft kills my blast."

Danny O'Rourke was sending out another call. The answer came from powerful sending instruments.

"Nitro squadron Hundred and One, on the fire!" it said, and gave a position in quick figures. Danny's own voice transmitter was on. He snapped out the position of the lone fighter. "Get in there!" he ordered; "Show your stuff! No—wait! Follow me; I'll lead you in!"

And to himself he added: "Now we'll see what pure nitrogen will do in a real scrap."

He closed a switch, and from a compartment at his back a low whine rose and grew to a scream. It was echoed in a shriek more shrill from the bow where a port had opened to take in the air. And Danny knew that that air, of which eighty percent was nitrogen, was being rid of its oxygen in the retort at his back, and the nitrogen alone was pouring out beneath him in a tremendous and ceaseless blast.

The squadron had appeared—a row of dots that came in on a long slanting drive from the ten thousand level. They swung into faultless formation to "ride his tail" into whatever flaming breath he might lead. And Danny O'Rourke threw his red ship down and into the valley 

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