But not for long. The treads whining in reverse, the robot whirled, scooping him up as it passed by. This time it didn't pause as it headed toward the edge of the dome. It was all his fault. The dome would seal itself after the robot plunged through, but not without loss of air--and one good mechanic. The machine churned on but surprisingly didn't plow heedlessly into the curved transparent wall. The extensibles felt the surface, the speed was checked and the direction changed. The robot moved parallel with the edge of the dome. It had a better sense of self-preservation than was common with robots of this type. It felt the wall as it rolled along. There was nothing noteworthy about the surface, smooth, hard, and slightly curved. Another extensible emerged from the squat body; the tip flashed a light toward the outside. It was strange out there. Jordan hadn't often seen it; not many people came to look out. When the asteroid was in the solar system jagged rocks had gleamed in the sharp light of the sun. But now the landscape was always dark except when some curious person wanted to remind himself what the rest of his world was like. It was a torn and crumpled sight the robot's light displayed, as if some giant had risen and tossed aside the rocks he slept in. But not completely rumpled; here and there were smooth areas that some vast engine might have planed flat--or the same giant had straightened out with a swipe of his hand before departing. The robot flicked off the light and turned away. Jordan breathed with relief when he saw where it was going, toward the central repair depot to which all robots returned periodically. It would slide into a stall and stop. He would get off. And he would see to it that the robot was thoroughly checked over before it was called out again. The entrance slot was extremely wide and equally low; it wasn't built for passengers on the robots. Momentarily the thought flashed across his mind that he should let himself be scraped off. But it seemed a precipitous way to dismount and anyway the machine would soon stop and he could get off more conventionally. Instinct won and Jordan flattened himself as they swept under the gate. He could feel the masonry twitching at his clothing. The slot opened into a circular space in which other robots were stationed in stalls. In the center were bins of spare parts. Jordan called out, not too hopefully. Robots were assigned from here on a broadcast band; he didn't think there were facilities for responding to the human voice. His machine headed toward a stall at the rear. This far from the entrance the light was dim. Jordan wondered why there was any light at all; robots didn't need it. Upon reflection he decided it was a concession to human limitations.