anywhere, except for the patches of brown earth.

CHAPTER XII

_Von Kettler's End_

Fredegonde took command, repressing her agitation with a visible
effort. "They cannot break down that door," she said, "and they dare
not ask for another key. It will take them a minute or two to go back
and reach us around the building. But there may be a score of people
watching us. Let us walk quietly toward the thickets. If I am present,
they will not suspect anything is wrong."

But Dick stood still, driven into absolute immobility by the
conflicting claims of duty. For overhead, high in the blue, was an
American dirigible.

And at his side was the President of the United States. One or other
of them he must sacrifice.

He chose. He ran forward without answering. Those squares of brown
earth, set side by side, were the airplane hangars, and he meant to
seize an airplane, if he could find one beneath its coat of
invisibility, and fly to warn the dirigible and the fleet.

A curious wind was blowing. It seemed to come swirling downward, as no
wind that Dick had ever known. It was growing in violence each moment,
beating upon his face.

As he ran, he was aware of Luke beside him. He heard shouting all
about them. Luke had been seen. Not only Luke, but Hargreaves, who was
running after Luke, with Fredegonde trying in vain to change his
intentions. At the edge of the first brown patch Dick collided
violently with the wall of the invisible hangar, and went reeling
back. The shouts were growing louder.

"Wait!" gasped Luke Evans. He had something like a large watch in his
hand. He held it out like a pistol, and from it projected a beam of
the black gas.

Then Dick remembered Colonel Stopford's words: "He showed me a watch
and said the salvation of the world was inside the case. I thought him
insane."

* * * * *

Insane or not, old Luke Evans had concealed the tiny model of the
camera-box to good purpose. As he swept the black beam around him, the
whole mass of buildings sprang into luminosity, the figures of a score
of men, grouped together, and advancing in a threatening mass, some
distance away--and more.

Two airplanes, standing side by side upon the tarmac, just in front of
the hangar--not mere pursuit planes, but six-seaters, formidably
armed, with central turrets and bow and rear guns, and propellers
revolving.

Two mechanics stood staring in the direction of the little group.

"