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."
"I read you loud and clear. So the objects are sent from Calvert's Favor, and they climb. They don't climb straight up, though. The wind carries them. The reason I think so is that the one I saw must have been driven by the wind, right down the creek toward me. It didn't climb until it got away from the funneling effect of the creek and into the river, then it went up pretty fast. At least it seemed to have risen fast when I looked over the top of the boat at it."
Scotty crunched an ice cube. "We're getting somewhere. There's only one kind of unpowered, vertical rising thing I know of. Are you with me?"