Before leaving the beach for the camp the boys walked to the point around which the boat had gone and scanned the lake and its shores through the field-glass. There was no sign of life anywhere, except where the birds swung from forest limbs back from the rim of the lake and called each other through the sultry air.
Reaching the camp after a weary climb, they did full justice to the meal which Pat had prepared, though the bacon and the hoecakes were stone cold, or at least as cold as anything could be in that glare of sunlight. Then, the dishes washed and the beds prepared for the night, they sat down to watch the lake and the sky to the south, for it was now the general belief that Ned would make his appearance with the aeroplane which had been promised by the government officials.
The point they had last visited, as well as the location of the fire, was in full view of the plateau, so the boys made no efforts to conceal their presence there. The men who had been observed in the boat must have noted their presence on the plateau before taking their leave. Perhaps, they reasoned, they had taken their departure because of this invasion.
The sun sank lower and lower in the sky, turning the plateau and the smooth waters of the lake to gold, still there were no signs of Ned, no indications of the return of the boat to the place from which it had been launched. Half an hour after dark, Frank, who was looking through the field-glass, caught sight of light in the south which did not appear to come from any star.
“Here he comes!” he cried. “That’s an aeroplane, all right!”
As the light drew nearer, traveling rapidly, the sharp explosions of the gasoline engine became audible. Then a light flickered over the upper plane, passed off, and swept the white surface again.
“How does he make that?” demanded Pat. “Looks like a great question mark.”
“That’s what it is,” Frank exclaimed. “Now, what does he mean by it?”
Chapter III.—JUST A TYPEWRITER RIBBON.
“I don’t understand what question he is asking,” Jack said, “but I know how he makes the signal. He has an electric flashlight, and he tips the plane—the upper plane—forward, like he was plunging to the earth, and writes the interrogation mark on the under side with the flame of the flashlight. See? Then it shines through the canvas and we read it! Great idea!”