where Tam hung
he could see billowing smoke clouds appear in every direction. Far
behind the enemy's lines at the great road junctions, in the low-roofed
billeting villages, on the single-track railways, they came and went.

The thunder of his engines drowned all sound so he could not hear the
never-ceasing booming of the guns, the never-ending crash of exploding
shell. Once he saw a heavy German shell in the air--he glimpsed it at
that culminating point of its trajectory where the shell begins to lose
its initial velocity and turns earthward again. It was a curious
experience, which many airmen have had, and quite understandable, since
the howitzer shell rises to a tremendous height before it follows the
descending curve of its flight.

He paid a visit to the only cloud that had any pretensions to being a
cloud, and found nothing. So he went over the German lines. He passed
far behind the fighting front and presently came above a certain
confusion of ground which marked an advance depot. He pressed his foot
twice on a lever and circled. Looking down he saw two red bursts of
flame and a mass of smoke. He did not hear the explosions of the bombs
he had loosed, because it was impossible to hear anything but the angry
"Whar--r--r--!" of his engines.

A belligerent is very sensitive over the matter of bombed depots, and
Tam, turning homeward, looked for the machines which would assuredly
rise to intercept him. Already the Archies were banging away at him, and
a fragment of shell had actually struck his fuselage. But he was not
bothering about Archies. He did swerve toward a battery skilfully hidden
behind a hayrick and drop two hopeful bombs, but he scarcely troubled to
make an inspection of the result.

* * * * *

Then before him appeared his enemy. Tam had the sun at his back and
secured a good view of the Mueller machine. It was the great white
dragon-fly he had seen two days before. Apparently Mueller had other
business on hand. He was passing across Tam's course diagonally--and he
was climbing.

Tam grinned. He was also pushing upward, for he knew that his enemy,
seemingly oblivious to his presence, had sighted him and was getting
into position to attack. Tam's engine was running beautifully, he could
feel a subtle resolution in the "pull" of it; it almost seemed that this
thing of steel was possessed of a soul all its own. He was keeping level
with the enemy, on a parallel course