cated mass of machinery.

Making as little noise as possible, we pushed ahead along the passage,
but when we had arrived within the distance of a dozen paces from the
inner end, we stopped, and Colonel Smith, getting down upon his knees,
crept forward, until he had reached the inner end of the passage. There
he peered cautiously around the edge into the chamber, and, turning his
head a moment later, beckoned us to come forward. We crept to his side,
and, looking out into the vast apartment, could perceive no enemies.

What had become of the sentinels supposed to stand at the inner end the
passage we could not imagine. At any rate, they were not at their posts.

The chamber was an immense square room at least a hundred feet in height
and 400 feet on a side, and almost filling the wall opposite to us was
an intricate display of machinery, wheels, levers, rods and polished
plates. This we had no doubt was one end of the engine which opened and
shut the great gates that could dam an ocean.

"There is no one in sight," said Colonel Smith.

"Then we must act quickly," said Mr. Edison.

"Where," he said, turning to Aina, "is the handle by turning which you
saw the Martian close the gates?"

Aina looked about in bewilderment. The mechanism before us was so
complicated that even an expert mechanic would have been excusable for
finding himself unable to understand it. There were scores of knobs and
handles, all glistening in the electric light, any one of which, so far
as the uninstructed could tell, might have been the master key that
controlled the whole complex apparatus.

"Quick," said Mr. Edison, "where is it?"

The girl in her confusion ran this way and that, gazing hopelessly upon
the machinery, but evidently utterly unable to help us.

To remain here inactive was not merely to invite destruction for
ourselves, but was sure to bring certain failure upon the purpose of the
expedition. All of us began instantly to look about in search of the
proper handle, seizing every crank and wheel in sight and striving to
turn it.

"Stop that!" shouted Mr. Edison, "you may set the whole thing wrong.
Don't touch anything until we have found the right lever."

But to find that seemed to most of us now utterly beyond the power of
man.

It was at this critical moment that the wonderful depth and reach of Mr.
Edison's mechanical genius displayed itself. He stepped back, ran his
eyes quickly over the whole immense mass of wheel