The beam from the unknown enemy snapped off as suddenly as it had come on, leaving, like lightning, an aching of the eyes behind it. Murray Lee swung his tank round, making for the reverse slope of the hill to avoid the light-beam. Crack! The beam came on again--right overhead this time. It flashed through the tree-tops leaving a trail of fire. He heard a torn branch bang on the roof of his tank, manipulated the gun to fire at the source of the beam and discovered that the magazine was empty. As he bent to snap on the automatic shell-feeding device, a searchlight from somewhere lashed out toward the black shape that opposed them, then went off. In the second's glimpse it afforded the enemy appeared as a huge, polished, fish-shaped object, its mirror-like sides unscarred by the bombardment it had passed through, its prow bearing a long, prehensible snout--apparently the source of the light-beam. Suddenly a shell screamed overhead and the whole scene leaped into dazzling illumination as it burst just between the enemy tanks and their own. It must be a shell from the dodos! The federated armies had no shells that dissolved into burning light like that. Then another and another, a whole chorus of shells, falling in the village behind them. Murray had a better look at their opponent in the light. It seemed to lie flush with the ground; there was no visible means of either support or propulsion. It was all of twenty feet in diameter, widest near the head, tapering backward. The questing snout swung to and fro, fixed its position and discharged another of those lightning-bolts. Off to the right came the answering crash as it caved in the armor of another of the luckless whippets. He aimed his gun carefully at the base of the snout and pulled the trigger; on the side of the monster there appeared a flash of flame as the shell exploded, then a bright smear of metal--a direct hit, and not the slightest damage! Ben Ruby's voice came through the radiophone, cool and masterful. "Pull out, folks, our guns are no good against that baby. I'm cutting off; radio positions back to the heavy artillery. Put the railroad guns on." Murray glanced through the side peep-hole again--one, two, three, four, five--all the American tanks seemed undamaged. The monster had confined its attention to the whippets, apparently imagining they were doing the shooting. He pulled his throttle back, shot the speed up, rumbling down the hill, toward the village. As he looked back, darkness had closed in; the brow of the hill, its rows of trees torn and broken by the light-beam stood between him and the enemy. Before him amid the flaring light of the enemy shells was a stir of movement, the troops seemed to be pulling out also.