On they sped, talking of the girls, of their plans for the summer, and
the coming examinations.

"Hark! What's that?" suddenly asked Paul, holding up his hand for
silence.

They were made aware of a curious, humming, throbbing sound.

"Some speed boat," ventured Dick.

"None in sight," objected Paul, with a glance up and down the river,
which at this point ran in a straight stretch for two miles or more.
"You could see a boat if you could hear it as plainly as that."

"It's getting louder," announced Innis.

Indeed the sound was now more plainly to be heard.

Paul gave a quick glance upward.

"Look, fellows!" he exclaimed. "An airship!"

The sound was right over their heads now, and as all three looked up
they saw, soaring over them, a large biplane, containing three figures.
It was low enough for the forms to be distinguished clearly.

"Some airship!" cried Dick, admiringly.

"And making time, too," remarked Innis.

Aircraft were no novelties to the cadets. In fact part of the
instruction at Kentfield included wireless, and the theoretical use of
aeroplanes in war. The cadets had gone in a body to several aviation
meets, and once had been taken by Major Franklin Webster, the
instructor in military tactics, to an army meet where several new forms
of biplanes and monoplanes had been tried out, to see which should be
given official recognition.

"I never saw one like that before," remarked Paul, as they watched the
evolutions of the craft above them.

"Neither did I," admitted Dick.

"I've seen one something like that," spoke Innis.

"Where?" his chums wanted to know, as Dick slowed down his boat, the
better to watch the biplane, which was now circling over the river.

"Why, a cousin of mine, Whitfield Vardon by name, has the airship craze
pretty bad," resumed Innis. "He has an idea he can make one that will
maintain its equilibrium no matter how the wind blows or what happens.
But, poor fellow, he's spent all his money on experiments and he hasn't
succeeded. The last I heard, he was about down and out, poor chap. He
showed me a model of his machine once, and it looked a lot like this.
But this one seems to work, and his didn't--at least when I saw it."

"It's mighty interesting to watch, all right," spoke Paul, "but we'll
be in for a wigging if we miss guard-mount. Better speed her along,
Dick."

"Yes, I guess so. But we've got time--"

Dick never finished that sentence. Innis interru