gan to roll
up toward the sun.

Suddenly out of the stillness came a faraway rumble like a fusillade of
cannon, now dying down low, again reaching such a height that it pained
the ears. Belated flying-machines darted across the sky here and there,
like storm-frightened birds, but they soon settled to earth. Every eye
was on the cloud which was now gashed with dazzling, vivid, electric
flashes. Thorndyke looked over the vast roof. He was alone. He walked to
the western parapet to get a broader view.

The clouds had increased till almost a third of the heavens were
obscured by the madly whirling blackness. There was a rumble in the
cloud, or beyond it, like thunder, and yet it was not, unless thunder
can be attuned, for the sound was like the music of a great orchestra
magnified a thousand-fold. The grand harmony died down. There was
a blinding flash of electricity in the clouds, and the Englishman
involuntarily covered his eyes with his hands. When he looked again the
blackness was covering the sun. For a moment its disk showed blood-red
through the fringe of the cloud and then disappeared. Total darkness
fell on everything.

The silence was profound. The very air seemed stagnant.

Then the wind overhead, by some unseen force, was lashed into fury, and
all the sky was filled with whirlpools of deeper blackness. Suddenly
there was a flash of soft golden light; this was followed by streams
of pink, of blue and of purple till the whole heavens were hung with
banners, flags, and rain-bows of flame. Again darkness fell, and it
seemed all the deeper after the gorgeous scene which had preceded it.
Thorndyke strained his sight to detect something moving below, but
nothing could be seen, and no sound came up from the motionless crowds.

Behind him he heard a soft footstep on the stone tiling. It drew nearer.
A hand was being carefully slid along the parapet. The hand reached him
and touched his arm.

It was the princess. "Ah, I have at last found you," she whispered, "I
saw you in the lightning, but lost you again."

He put his arm round her and drew her into his embrace. He tried to
speak, but uttered only an inarticulate sound.

"I could not possibly come earlier," she apologized, nestling against
him so closely that he could feel the quick and excited beating of
her heart. "My father kept me with him till only a moment ago. Captain
Tradmos will be here soon."

"When do we start?" he asked.

"That is the trouble,"