The balance of that night and all of the following day Nur An and I labored without rest until we had fashioned an enormous bag from the fabric that had covered the walls and ceiling of our cell and from the scraps that remained we fashioned long ropes and when night fell again our task was completed.

"May luck be with us," I said.

"The scheme is worthy of the mad brain of Ghron himself," said Nur An; "yet it has within it the potentialities of success."

"Night has fallen," I said; "we need not delay longer. Of one thing, however, we may be sure, whether we succeed or fail we shall have escaped the fire and in either event may our ancestors look with love and compassion upon Sharu, whose friendship has made possible our attempt."

"Whose love," corrected Nur An.

Once again I made the perilous ascent to the roof, taking one of our new made ropes with me. Then, from the summit, I lowered it to Nur An, who fastened the great bag to it; after which I drew the fruits of our labors carefully to the roof beside me. It was as light as a feather, yet stronger than the well tanned hide of a zitidar. Next, I lowered the rope and assisted Nur An to my side, but not until he had replaced the bar that we had removed from the window.

Attached to the bottom of our bag, which was open, were a number of long cords, terminating in loops. Through these loops we passed the longest rope that we had made—a rope so long that it entirely encircled the circumference of the tower—when we lowered it below the projecting eaves. We made it fast there, but with a slip knot that could be instantly released with a single jerk.

Next, we slid the loops at the end of the ropes attached to the bottom of the bag along the cord that encircled the tower below the eaves until we had maneuvered the opening of the bag directly over the mouth of the flue leading down into the furnace of death in the pits of Ghasta. Standing upon either side of the flue Nur An and I lifted the bag until it commenced to fill with the hot air rushing from the chimney. Presently it was sufficiently inflated to remain in an erect position, whereupon, leaving Nur An to steady it, I moved the loops until they were at equal distances from one another, thus anchoring the bag directly over the center of the flue. Then I passed another rope loosely through the loops and secured its ends together, and to opposite sides of this rope Nur An and I snapped the boarding hooks that are a part of the harness of every Barsoomian warrior, the primary purpose of which is to lower boarding parties from the deck of one ship to that of another directly below, but which in practice are used in countless ways and numerous emergencies.

Then we waited; Nur An ready to slip the knot that held the rope around the tower beneath the eaves and I, upon the opposite side, with Sharu's sharp dagger prepared to cut the rope upon my side.

I saw the great bag that we had made filling with hot air. At first, loosely inflated, it rocked and swayed, but presently, its sides distended, it strained upward. Its fabric stretched tightly until I thought that it should burst. It tugged and pulled at its restraining cords, and yet I waited.