Closer to the shore of the lake, the meadow gave way to trees. This was one of the more mature forests on New Earth. It had been seeded only a few years after the First Treaty, about a hundred years ago. She pulled the nose up, skimmed over the highest branches, then dropped again until she was gliding over the blue water of the lake: the melted core of a comet, still coming alive with seeded algae and fish. With a voice command she caused the glider to drop a tube, no thicker than her finger, into the water skimming by a few meters below. On her first pass across the lake’s diameter she collected twenty kilograms of water, which slowed the glider down somewhat. She found a thermal on the other side and rode it up a few hundred meters before rolling over and diving down for another, faster pass over the lake, and another long drink of water. This part of the journey was the most ticklish, so it was good that it came first, when she was still fresh. A glider that was light enough to carry around on her back was, by the same token, too light to store very much kinetic energy. Its lack of momentum placed limits on the maneuvers Kath Two could perform in the higher atmosphere; small twitches in the flow of air would bat it around like a feather. It needed to get a lot heavier. The way to do that was to scoop water out of a lake, as she was doing now. But it all happened at low altitude and low speed, where the margin for error was slender. The first few passes, when the glider weighed practically nothing, were the most delicate. So she took her time at each side of the lake to find good thermals and harvest their force. After an hour of that, however, she was dive-bombing her way across the crater with terrific authority, carrying hundreds of kilograms of ballast in the belly and the wings. By then she had learned where to hunt for thermals that, as the morning wore on, bloomed with increasing vigor from the open meadows in the shoulders of the great crater.