Among the things connected to the furnace in Pittsburgh Sector Ten was a small sampling pipe that carried away a continuous stream of white-hot combustion products for on-line analysis. The sampling pipe left the furnace through a flange located next to a large valve assembly that regulated the flow of exhaust gases from the furnace to a heat exchanger used to raise steam for use elsewhere. The valve was biased to fail-safe by means of a powerful spring, which meant that if a fault occurred anywhere in its control system it would automatically close to the safe position.
During the firefight that had taken place in that part of Pittsburgh, a stray bullet had smashed the pin that secured one end of the pivot arm attached to the spring, causing the arm to snap back toward the sampling pipe. In doing so it sheared off the head of one of the bolts that held the flange and was finally brought to a stop hard against the pipe itself. Thus there was only the second, overstrained bolt and the thin material of the pipe wall, softened by the heat inside it, to oppose the fierce pull of the spring against the pivot arm.
The sampling pipe snapped at the moment when Private Dringham of the damage inspection party was drifting past on his way to check some nearby high-voltage insulators. The blast of incandescent gas hit part of a motor mounting and sprayed off in all directions, scorching the left side of Dringham's body from the shoulder to the knee.
The first anyone else knew about it was when they heard a scream accompanied by a sudden pulsating hiss of escaping gas at high pressure. Every face in the vicinity whirled around to see a figure hurtling back, trailing smoke from its uniform, away from a tongue of flame that had gushed from the furnace wall. Within seconds they had launched themselves toward him and while two soldiers caught him to check his flight, another arrived with an extinguisher and plastered one side of him with foam. The medics who had been attending to the casualty in A Section wrapped him in a fire blanket, administered a tranquilizer shot and steered the now inert form gently away toward the entrance to the access shaft.
And from the shadows above the top of the furnace, a sphere drone observed.
In one of the fields out by the north edge of Sunny-side, a robot harvester chugged slowly along the furrows, digging up the sweet potatoes that were ready for eating and meticulously avoiding the seedling soybeans interplanted for optimum yield. A group of off-duty technicians from the Agricultural Division's nearby buildings were sitting around a few feet away from their parked roughrover and watching idly from the grassy bank that fringed the field.
"That's all I know," Sally Linse said, shrugging from where she was lounging near the top of the bank. "About an hour ago there was some shooting somewhere in Detroit. I heard there were some casualties there too."
Mike Sclorosi nodded as he chewed on a straw.
"I heard something like that too. Does that mean it's started attacking people?"
"Wouldn't think so," Art Grayner replied dubiously from where he was perched next to Sally. "If that were the case we'd have heard about it. The story's probably been exaggerated somewhere along the line."
"Then why are we carrying weapons permanently now?" Sally demanded. To me, that would indicate there's more than just talk behind it."
"It's just a precaution, like they said," Art insisted. "In case anything like that starts. Wouldn't you rather be ready for it?"
Mike turned his head away and shouted in the direction of the rover.
"Hey, Paul. What's keepin' ya? Did you find those Cokes in there yet?" One of the two heads visible in the back of the rover looked up and called out over the open tailgate.
"Give me a minute, willya. What's the matter—you dying of thirst or something? I'm looking for the cigarettes."
Another girl, standing on top of the bank on the other side of Sally, was staring out over the terraced rice paddies behind them where the floor of the Rim began rising more steeply to become one of the walls.
"Uh uh," she said. There was an ominous note to her voice. The others looked up.
"What is it, Carol?" Mike asked.
"Drones. Fairly high up and heading this way. What would they be heading this way for?"
The others scrambled to their feet and looked out over the bank. Four dots were skimming along over the terraces toward them and growing larger by the second.
"What's the big attraction?" Paul called from the rover. Art told him.
"Stand to," Mike shouted. "Don't take chances." Within ten seconds the four on the bank had seized their rifles and taken up defensive positions around the vehicle. Paul and Connie heaved a couple of remote-control packs out of the back and up onto the roof, climbed up after them and launched two destroyers from the racks above the driver's cab. The destroyers moved forward to hover ten feet above the bank, between the rover and the approaching drones.
The four drones slowed in their flight and spread out to form a wide semicircle. They seemed to be keeping their distance at about two hundred feet. The defenders watched and waited, their faces betraying mounting tension. Then the two hovering destroyers suddenly went berserk, plunging and bucking in chaotic random motions. One plowed into the ground and died while the other reared in and out of sight as it cavorted wildly on the far side of the bank.
"What the—" Mike began, but Connie cut him off.
"I can't hold it. Something's screwing up the beam."
"The digger!" Art shouted. "It's going crazy!" They stared incredulously at the field on the side of them away from the bank. The harvester was thrashing around in wild circles and throwing clouds of soil randomly into the air.
"Sally, get on to Base," Mike called. "Tell 'em there's something crazy going on here. Art, keep an eye on that looney digger." Sally vaulted nimbly into the rover and began frantically operating the communications equipment inside.
"I can't get through," she called out after a few seconds. "All channels are jammed up with garbage."
The second destroyer flopped down on its back and lay buzzing fitfully. The drones began maneuvering to adjust their positions as if experimenting with various configurations, but made no attempt to come in closer or to try anything overtly hostile. After a while Mike lowered his rifle and rested it on one of the front wheel guards, all the time studying the drones intently through narrowed eyes.
"Must be an ECM team," Art decided. "They're testing out ways of jamming our systems."
After about five minutes the flight of drones about-turned and flew off in the direction from which they had come. The digger promptly recovered its sanity and carried on as if nothing had happened and the paralyzed destroyer came back to life and returned to its rack. The one that had made the nose dive remained dead. Mike and Art climbed the bank and walked over to examine it.
"At least it knows now that we're not radio-controlled," Mike murmured half to himself. Art gave him a funny look.
"What the hell are you talking about?" he asked;
"I'm not sure," Mike said in a strange voice. "It's just that I had the spooky feeling that they weren't trying to screw around with our systems at all. That was just an accident. I reckon they were trying to see if they could jam us!"
Three similar incidents were reported all at about the same time. In Berlin a squadron of drones disrupted communications and robot-control systems over a small localized area but went away again soon afterward. An Air Force major who was present stated that he too had formed the distinct impression that the drones had been watching for signs of any reaction on the part of the humans in the vicinity, not the machines.
A large number of drones appeared over the shopping precincts of Downtown, their curiosity evidently having been aroused by the crowds there. In the course of another futile people-jamming experiment, a nervous sergeant ordered his men to open fire with rifles after the precinct had been evacuated. Four drones were brought down immediately and the rest retired at once. It was an easy victory since the drones involved were not the armored variety that had made their first appearance earlier in Pittsburgh.
Although Spartacus seemed by this time to have had its back forced hard against the wall, these latest developments held a significance that several of the scientists, Dyer included, found ominous. So far, Spartacus had exhibited no means of acting offensively or even of knowing how to if it could. But if the interpretations of its latest behavior were correct, it was beginning to look around for ways of doing something about things other than itself which it appeared to be just starting to recognize within its environment, and which, seemingly, it had linked with all the things that had been plaguing it. It was forming the notion that perhaps prevention might be better than cure, and was exploring for ways of achieving it.
Its first experiments, which were logical things to try by a machine that was itself highly susceptible to electronic methods of interference, had failed to work. How long would it be before it discovered something that did?