"You're probably wrong," Jak snorted, and their mother interrupted what she thought was the beginning of another of their interminable arguments. "Are you going to land here, or go on to another planet first?" she asked Jon. "I'm going low enough to test atmosphere and temperature before I decide," he told her. "Well," resignedly, "do as you boys think best." Jon manipulated his controls and as the ship tilted slightly, they could see in their plates the ground coming closer. Slowly, under the increased reaction of the powerful bow tubes, the ship slowed until it was cruising at about one thousand miles an hour and about a mile above the surface--or the tops of the vegetation, at least. Then Jon leveled it off. "You know how to test atmosphere, Jak?" he asked. "The temp now is about 99.4 degrees Fahrenheit, so it probably isn't over 110 at ground level." "Yes, Father taught me that." Jak moved over to the hull wall where there was an atmosphere-trap and the mechanism that tested and recorded the contents of any air they might encounter on a new planet. He worked this and studied the results. This latest invention of Terran aeroscopic technies was simple to operate. A chart, already prepared to show the constituents of Earth's atmospheric limits compatible to human needs, was placed beneath a stylus. The latter drew a curve showing the components of the new air, and if the lines did not go above or below the red one on the prepared chart, the atmosphere was safe for human consumption. "Carbon dioxide a little higher, and when I tested density with a spring balance the ten-pound weight showed nine and a half," Jak reported. "That means we'll feel a trifle lighter, and won't find walking and lifting as hard." Their mother had been hovering nervously in the background. Now she stepped up and asked, "Are you sure it is safe here?" "We will be before we go outside, Mother," Jak assured her, then turned to Jon. "Where are you going to land?" "Soon as I find a good spot. Keep your eyes peeled for a large clearing." But they had gone only a few more miles when Jak yelled, "There, Jon! Off to the left a mile or so." At his first words Jon had increased the negative acceleration. His darting eyes spotted the clearing, and he put the ship into a circle and elevated the nose so they climbed to a height of some twenty miles. "Grab that astrogation book and get ready to read me the checks, Owl. Mom, you strap in. Is Pop all right?" Mrs. Carver assured him that on her recent trip to her husband's bunk she had seen to it that he was safely fastened down, in anticipation of their landing. Jak picked up the book and opened it to the book-marked page. He sank into the co-pilot's seat, and fastened the safety belt. "Ready when you are." Their mother now reported, "All fast, Jon." A moment while the younger boy glanced quickly at his various dials, then he said tensely, "Shoot." "Check decelerometer." "On the hairline."