For the remainder of the day, between breaks for meals, checks on the patients, and a period of rest for himself, they watched the glider overhead because there was nothing else of interest happening. The spider aircraft was doing some very interesting things, like signaling to its mother ship on the other side of the island and the three vessels drawn up along the beach.
A large, circular panel close to one wing-root had opened and begun spinning in the slipstream about its two diametrically opposed attachment points. One face of the panel was bright yellow while the other matched the overall brownish-green color of the glider. The rotating disk was within easy reach of the pilot who used one of its forelimbs to check the spin at irregular intervals to show either the light or dark face to watchers below and on its more distant mother ship.
“Ingenious,” said the captain admiringly. “It’s using the visual equivalent of Earth’s old-time Morse code. The spiders might not have radio but they can communicate over short to medium distances. The rotating panel would have minimum effect on the glider’s flight characteristics, and any information being transmitted would be passed slowly, although if necessary the message could last for as long the glider remained aloft. Judging by the pauses in signaling, which last for anything up to fifteen minutes, I’d say that there is a similar device on the mother ship and they are talking about us.”
“Sir,” said Haslam. “It’s not heading back to its ship. Why is it still climbing? I would have expected it to come down to take a closer look at us so that the pilot would have more to talk about.”
The captain exercised the prerogative of a senior officer who did not know the answer by maintaining a commanding silence.
The litters bearing all of the patients were moved into the afternoon sunshine of the beach although, as it had been in the recovery ward, the druul-like Earth-human casualties and those from the Trolanni searchsuit were separated from visual contact by portable screens. There were a few spiders moving about the beach, but they stayed close to their ships and it was plain that another attack was not imminent. To conserve power the meteorite shield had not been deployed so that the patients could benefit from the sea breeze as well as the sunshine. They, too, lay watching and talking about the slowly ascending glider. It was still climbing late in the afternoon when the patients were moved indoors and when the sun began to sink behind the high ground inland. When dusk fell at ground level it was still climbing, tiny with distance but clearly visible in the bright, orange light of the sun which for it had not yet gone down. It began circling widely and performing slow, intricate aerobatics.
“Doctor,” said the captain, “I’m beginning to worry about what our flyboy is doing up there. Its present altitude is close on five thousand meters and it must be cold up there. In the circumstances of the recent attack it doesn’t seem appropriate for it to be showing off and selfishly enjoying itself like this. It’s possible that it is performing some form of sunset religious ritual that the spiders, or maybe only their glider pilots, believe is important, but I don’t think so.”
“What do you think, friend Fletcher?” said Prilicla.
“The glider is far too high for its swiveling wing panel to be readable without a telescope,” the captain replied, “and I can’t imagine a species so afraid of fire as are the spiders being able to use it to process sand into glass and cast lenses. My theory is that the aerobatics are another form of signaling,”
It paused for a moment as if expecting an objection, then went on, “Of necessity the vocabulary would have to be restricted because there are only so many ways that a glider can move in the air, so its report would have to be simplified, couched in stock phrases that would be much less detailed than the visual Morse, and yet it is trying to describe happenings unique in its species’ experience. But that high-flying aircraft and its message will be visible over a much greater distance than the shorter-range but more fluent swiveling wing-panel arrangement.”