which we had blown in this network with the disintegrators
had been made noiselessly, and Mr. Edison believed, since no enemies had
appeared, that our operations had not been betrayed by any automatic
signal to watchers inside the building.

Consequently, we had every reason to think that we now stood within the
line of defense, in which they reposed the greatest confidence, without
their having the least suspicion of our presence.

Aina assured us that on the occasion of her former visit to the power
house there had been but two sentinels on guard at the entrance. At the
inner end of a long passage leading to the interior, she said, there
were two more. Besides these there were three or four Martian engineers
watching the machinery in the interior of the building. A number of
airships were supposed to be on guard around the structure, but possibly
their vigilance had been relaxed, because not long ago the Martians had
sent an expedition against Ceres which had been so successful that the
power of that planet to make any attack upon Mars had, for the present
been destroyed.

Supposing us to have been annihilated in the recent battle among the
clouds, they would have no fear or cause for vigilance on our account.

The entrance to the great structure was low--at least, when measured by
the stature of the Martians. Evidently the intention was that only one
person at a time should find room to pass through it.

Drawing cautiously near, we discerned the outlines of two gigantic
forms, standing in the darkness, one on either side of the door. Colonel
Smith whispered to me:

"If you will take the fellow on the right, I will attend to the other
one."

Adjusting our aim as carefully as was possible in the gloom, Colonel
Smith and I simultaneously discharged our disintegrators, sweeping them
rapidly up and down in the manner which had become familiar to us when
endeavoring to destroy one of the gigantic Martians with a single
stroke. And so successful were we that the two sentinels disappeared as
if they were ghosts of the night.

Instantly we all hurried forward and entered the door. Before us
extended a long, straight passage, brightly illuminated by a number of
electric candles. Its polished sides gleamed with blood-red reflections,
and the gallery terminated, at a distance of two or three hundred feet,
with an opening into a large chamber beyond, on the further side of
which we could see part of a gigantic and compli