It was heart-breaking work to keep the fires going with charcoal, because it burned so rapidly in the powerful draft of the furnaces, but the original fire-room gang had been recruited to several times its original number from among the towerites, and the work was divided until it did not seem hard.

As Estelle looked down two tiny figures sauntered across the clearing from the woods with a heavy animal slung between them.  One of them was using a gun as a walking-stick.  Estelle saw the flash of the sun on its polished metal barrel.

There were a number of Indians in the clearing, watching with wide-open eyes the activities of the whites.  Dozens of birch-bark canoes dotted the Hudson, each with its load of fishermen, industriously working for the white people.  It had been hard to overcome the fear in the Indians, and they still paid superstitious reverence to the whites, but fair dealings, coupled with a constant readiness to defend themselves, had enabled Arthur to institute a system of trading for food that had so far proved satisfactory.

The whites had found spare electric-light bulbs valuable currency in dealing with the redmen.  Picture-wire, too, was highly prized.  There was not a picture left hanging in any of the offices.  Metal paper-knives bought huge quantities of provisions from the eager Indian traders, and the story was current in the tower that Arthur had received eight canoe-loads of corn and vegetables in exchange for a broken-down typewriter.  No one could guess what the savages wanted with the typewriter, but they had carted it away triumphantly.

Estelle smiled tenderly to herself as she remembered how Arthur had been the leading spirit in all the numberless enterprises in which the castaways had been forced to engage.  He would come to her in a spare ten minutes, and tell her how everything was going.  He seemed curiously boylike in those moments.

Sometimes he would come straight from the fire-room—­he insisted on taking part in all the more arduous duties—­having hastily cleaned himself for her inspection, snatch a hurried kiss, and then go off, laughing, to help chop down trees for the long fishing-raft.  He had told them how to make charcoal, had taken a leading part in establishing and maintaining friendly relations with the Indians, and was now down in the deepest sub-basement, working with a gang of volunteers to try to put the building back where it belonged.

Estelle had said, after the collapse of the flooring in the board-room, that she heard a sound like the rushing of waters.  Arthur, on examining the floor where the safe-deposit vault stood, found it had risen an inch.  On these facts he had built up his theory.  The building, like all modern sky-scrapers, rested on concrete piles extending down to bedrock.  In the center of one of those piles there was a hollow tube originally intended to serve as an artesian well.  The flow had been insufficient and the well had been stopped up.