* * * * *

Dirk swooped straight down at the leviathan which lay so quietly on the
surface of the Sound and then slowly circled around it. No sign of an
aperture of any sort could be seen in the craft. Then he dropped the
plane lightly on the water, close to the metallic monster, which towered
fully four hundred feet above them, despite the fact that more than half
of it was submerged.

"It must be hollow," remarked Steinholt, "or it wouldn't be so far out
of the water. In fact, it most certainly would sink, if it was solid."

At the touch of a lever which lay under one of Dirk's hands the plane
rose straight out of the water, and he maneuvered it directly over the
top of the strange enigma. Then he touched a button and the pontoons
were drawn up into the undercarriage of the craft.

"Shall I make a landing on it?" he asked, turning his head and
addressing Fragoni.

The latter nodded his head, and Dirk dropped the ship gently onto the
smooth surface of the monster, the pneumatic gearing completely
absorbing the shock of the landing.

Dirk relinquished the controls and, opening the door of the cabin, he
stepped out onto the rough and pitted substance of which the leviathan
was compounded. He stood there while the others came out after him.

A large area on the top of the monster was perfectly flat and, within a
very few moments, Dirk discovered that it was decidedly warm. He had
brought the plane down close to the middle of the length of the strange
craft in the belief that there, if anywhere, some indication of an
entrance might be found.

* * * * *

The voice of Steinholt, tense with suppressed excitement, appraised him
that his surmise had been correct.

"There is a manhole of some sort," the electrical wizard exclaimed. "And
look, it is turning!"

They saw, not far ahead of them, a circular twelve-foot section of the
deck slowly revolving, and, even as they watched, it commenced to rise
slowly upward as the threads with which it was provided turned gradually
around.

Almost involuntarily they retreated a few feet and stood there,
spellbound, as they stared at the massive, revolving section of the
deck.

It continued to turn until fully ten feet of the mobile cylinder had
been exposed. Then the bottom of it appeared. Even then it continued to
revolve and rise on a comparatively small shaft which supported it and,
at the same time, thrust it