Hal laughed.

“Oh, you will be all right directly,” he said.  “For my part, I like it.”

“How fast do you suppose we are going?”

“About fifty miles an hour.”

“Great Scott!  That’s going some!”

The machine was skimming at great speed through the air, flying low, as Hal did not wish to lose sight of the ground entirely.

“This is high enough for me,” he explained.  “I might want to go down suddenly, and I want to see where I am going.  Of course, if it is necessary, we will go higher.”

“I guess we might as well fall ten miles as to fall from here,” remarked Chester.  “If anything went wrong it would be good night for us.”

For a time they flew along in silence.

Suddenly there was the sound of a shot from below, and a bullet whizzed by the flying aeroplane.

Hal sent the machine higher into the air with a jump, and Chester let out an exclamation as he was almost thrown from his seat.

“That was too close for comfort!” cried Hal.

“Well, the next time you decide to shoot up like that, let me know first!” exclaimed Chester.  “You almost lost me that time!”

“Hang on tight!” shouted Hal.  “You never can tell what will happen with me running this thing, so don’t take any chances.”

“I’ll hang on tight in the future, never fear,” was the reply.  “What do you suppose that shot was?”

“Some sentry, I suppose.  I guess he knew no machine was supposed to be flying around here.  That’s probably why he took a shot at us.  We were flying too low, anyhow.  We will stay up here, where we can’t be so easily seen or heard.”

For some time the boys sailed along without a word, and then, just as Chester opened his mouth to ask Hal where he supposed they were, there was the sound of rushing wings, and, turning in his seat, Chester beheld a huge shape rushing after them.

“Speed up, Hal!” cried Chester.  “We are pursued!”

Without stopping to ask questions, Hal threw the speed lever over, and the machine leaped forward like some live thing.

At the same moment there came the crack of a rifle, and, as Hal dropped one arm from the steering wheel the aeroplane rocked crazily and dived toward the ground.

The bullet had grazed Hal’s left shoulder.

With a desperate effort, the lad righted the machine with his one good arm, and it shot upward again.

“What’s the matter?” gasped Chester.  “Are you hurt?”

“Hit in the shoulder,” replied Hal briefly.  “I suppose whoever fired aimed at the machine.  I just happened to be in the way, that’s all.”

“But you can’t drive with one arm!  Hadn’t we better—­”

“Can’t!” exclaimed Hal.  “I’ve got to!”

At that moment both boys were almost blinded by the glare of a dazzling light directly ahead!

CHAPTER XI.