.

"Radite!" bellowed Dr. Bird to Carnes. "Imagine the effect if that had
been a full charge fired from a completed Breslau gun! Watch the
planes, now. I think they are going to drop a few eggs on them."

* * * * *

The black mist cleared as if by magic and the platform was in plain
view. The big glass dome rolled back into place as the two planes
swept over at an elevation of two thousand feet. From each one a
small black cigar-shaped object was released and fell in a long
parabola toward the earth. The glass dome which had been closing over
the gun platform rolled quickly back and a long beam of intense
blackness pierced the heavens. First one and then the other of the
falling bombs disappeared from view into it, and then the black column
faded from view. The two bombs fell with increasing speed but the dome
closed over the platform before they struck. The two hit the dome at
almost the same instant and instead of the blinding crash they
expected, the watchers saw the bombs rebound from the dome and fall
harmlessly into the water.

"Stymied!" muttered the doctor. "I wonder what other properties that
confounded lamp has."

He resumed his advance, Carnes and the soldiers keeping abreast of
him. When they were within two hundred yards of the platform it rose
again and the transparent dome rolled back. A beam of black shot forth
over the swamp, searching them out and hiding them from view. First
one and then another felt the effects of the black beam; but the
vitrilene which the Doctor had provided stood them in good stead, and,
aside from a slight shortening of their breath, none of the attackers
felt any the worse.

"Come on, men!" cried the Doctor as his athletic figure plowed forward
through the breast-deep water. "That is their worst weapon and it is
harmless against us!"

Cheering, they fought their way toward the platform. It sunk for a
moment and then rose again. As the dome swung back a sharp crackle of
machine-gun fire sounded and the water before them was whipped into
foam by the plunging bullets. One of the soldiers gave a sharp cry and
slumped forward into the water.

"Fire at will!" shouted the lieutenant in command.

* * * * *

A crackle of rifle fire answered the tattoo of the machine-gun, and
the sharp ping of bullets striking on the dome could be plainly heard.
An occasional shot kicked up a spurt of white dust from the concrete,