"I carry a message from our commander to a detachment stationed further on!" But the sentinel, catching sight of his uniform, and exclaiming: "A Johnny Reb!" threw up his rifle and fired.

Luckily for Harry it was such a hurried shot that the bullet only made his flesh creep, and passed on, cutting the twigs.

Then Harry lifted himself up and ran.
Lifting himself up describes it truly.

He had all the motives which can make a boy run, pressing danger, love of life, devotion to his cause, and a burning desire to do his errand.

Hence he lifted his feet, spurned the earth behind him and fled down the slope at amazing speed.
Several more shots were fired, but the bullets flew at random and did not come near him.
Harry did not stop until he was two or three miles from the fort, when he knew that he was safe from anything but a chance meeting with the Northern troops.