avoid several little errors of judgment, not much in themselves
possibly; but which tended to interfere with his doing the one thing
necessary--firing point blank into the muffled face of the German pilot.

Once more were they rushing headlong toward each other. Tom was steadier
now, and more alert. He had his plan of campaign mapped out clearly in
his mind. He had moreover noticed a weak point about the other's method
of attack, of which he intended to take advantage.

The other three Americans were just as hotly engaged not far away; but
it was a case of every man for himself. Tom counted on receiving no
assistance. Indeed, while that feeling of confidence pulsed through his
veins he would have scorned to call for help, or even to allow it, if he
could prevent such a thing.

Again the guns opened fire as the two foes advanced with savage fury.
Such a battle in the clouds is on a plane that almost beggars
description. Nothing resembling it has ever been known before in all the
annals of history until the present world war broke out, and the
airplane was perfected as it stands to-day.

This attack was even more tumultuous than the first had been. The planes
tried dodging, and several tricks were brought to bear on either side;
for it seems that every pilot has his pet theories as to how best to
catch an opponent napping. Everything is fair, once the battle royal has
started and German wit is matched against American, or French.

Again did they pass each other for a sudden dip. Each feared to be
caught in a condition that would not permit of defense. They looked for
all the world like a couple of agile boxers engaged in a contest, in
which foot-work counted almost as much as that of the fists.

Around and around they flew, coming back to the attack a third, and even
a fourth time. Tom was beginning to grow impatient. Try as he could, he
did not seem able to bring the other down, though he was almost sure he
had poked his rapid-fire gun straight for the German's face, and when
only a comparatively short distance away.

"I've got to get him!" he muttered. "Or else he'll get me!"

He wondered whether there could be anything in what he had heard one old
aviator say, to the effect that he firmly believed some of those Germans
must be wearing armor or suits of mail, since he had poured streams of
missiles straight at them, and without the least appreciable effect.

The German was getting a bit reckless. No doubt he ha