The valve assembly, traveling with bullet speed, barely missed Scotty's head
Scotty yelled, "Run!"
The tank, its air free to escape, writhed and turned, then fell over on its side. It was like an inflated balloon, turned loose to fly around a room. Air jetted from it with terrific velocity, so that the tank was, for the period while its air lasted, a true rocket.
It struck the wall of the shed and went through it like paper, smashed into a stud and caromed slightly, so that its trajectory was altered enough to drive it directly at Rick. He fell flat and it went over, just grazing him, then flew into the palm grove. It hit a palm a slanting blow and turned upward, shooting high in the air, clipping off the top of another palm as it went.
As the boys watched, horrified, it climbed straight up. Then, its high pressure nearly exhausted, it turned leisurely and plunged back into the grove, almost burying itself in the sandy soil.
The boys sat down and stared weakly at each other. For the first time, Rick noted that Scotty's hand was bleeding. He said shakily, "Here, let me look at that."
The scientists rushed out of the house and demanded to know what had happened. The tank had blown through its devastating course so fast that they had not even had time to get outdoors.