Rick was physically relaxed, but mentally active. It was characteristic of him that he never let go of a puzzle until he had found a solution, or had tried all possibilities and been forced to admit defeat. He was a long way from defeat at the moment. The case of the flying stingaree was just getting interesting. "What are the flying stingarees?" he asked quietly. Scotty shifted position in his chair and looked at Rick quizzically. "You don't expect an answer. But I can tell you a few things they are not." "Tell away," Rick urged. "They are not flying saucers, aircraft, kites, sting rays, birds, fish, or good red herrings. Beyond that, deponent sayeth not, as the legal boys say." "Uh-huh. And why are they not flying saucers?" "For the same reason they're not aircraft. If you recall all the talks with people who've seen them, they don't maneuver, and they don't travel very fast. They appear--or they're noticed, let's say--and they just get smaller and smaller until they vanish. They move, but not much." Rick nodded. "The circle we drew around all the sightings doesn't cover a very large territory. All the sightings have been within that circle. People had to look toward Swamp Creek to see the objects. Yet, they did something interesting. They grew smaller. What makes things seem to grow smaller?" "Apparent size decreases with distance," Scotty replied promptly. "Sure. And how do you get distance, when the sightings are all within a circle only a few miles in diameter?" "Only one way. With altitude. The things had to be going up." Rick agreed. "That's how I figure it, too. It also explains why the circle of sightings is so small. Above a certain altitude, the objects are no longer visible. Or they're not so visible that they attract attention. I suppose we could work out some calculations. How large an object can be seen readily at what distance? Then we could apply a little trigonometry and figure their size." "We could," Scotty agreed, "but do we need to? Let's assume the object you saw was typical. How big was it?" Rick thought it over. He had had only a quick glimpse, and the background had been the gray of the storm. His vision had been obscured because of the rain. "Maximum of ten feet across and maybe eight tall. It was probably less." "Okay. So the reason sightings are confined to this area is because the objects are fairly small. When people see them, they're relatively close, and fairly low. Even the small planes that fly from the airfield are much bigger than the flying stingarees, but when the planes go over at about five thousand feet, they seem tiny. At that altitude the flying stingarees must be at the limit of really good visibility."