s
evident from the fact that it was perceptibly traversing the Moon's
surface. Perhaps it was travelling at the rate of fifty thousand miles
an hour.

Brent, the chief officer, burst up the companion. His face was livid.

"Black ship approaching us from the Moon, Sir," he stammered.
"Benson's training his guns, but it must be twenty thousands miles
away."

"Yes, even our ray-guns won't shoot that distance," answered Nat.
"Tell Benson to keep his guns trained as well as he can, and open fire
at five hundred."

Brent disappeared. Madge and Nat were alone on the bridge. Nat was
shouting incomprehensible orders down the tube. He stopped and looked
up. The shadow of the approaching ship had crossed the Moon's disk and
disappeared.

"Well, young lady, I think your goose is cooked," said Nat. "If I'm
not mistaken, that ship is Axelson's, and he's on his way to knock us
galley-west. And now oblige me by leaving the bridge."

"I think he's a perfectly delightful character, to judge from that
message he sent you," answered Madge, "and--"

Brent appeared again. "Triangulation shows ten thousand miles, Sir,"
he informed Nat.

"Take control," said Nat. "Keep on the gyroscopic course, allowing for
aberrancy, and make for the Crater of Pytho. I'll take command of the
guns." He hurried down the companion, with Madge at his heels.

* * * * *

The gunners stood by the ray-guns, three at each. Benson perched on a
revolving stool above the batteries. He was watching a periscopic
instrument that connected with the bridge dome by means of a tube, a
flat mirror in front of him showing all points of the compass. At one
edge the shadow of the black ship was creeping slowly forward.

"Eight thousand miles, Sir," he told Nat. "One thousand is our extreme
range. And it looks as if she's making for our blind spot overhead."

Nat stepped to the speaking-tube. "Try to ram her," he called up to
Brent. "We'll open with all guns, pointing forward."

"Very good, Sir," the Cockney called back.

The black shadow was now nearly in the centre of the mirror. It moved
upward, vanished. Suddenly the atomic motors began wheezing again. The
wheeze became a whine, a drone.

"We've dropped to two thousand miles an hour, Sir," called Brent.

Nat leaped for the companion. As he reached the top he could hear the
teleradio apparatus in the wireless room overhead begin to chatter:

"A-A-A. Don't try to interfere. Am t