ll be able to do it, anyhow. But it's worth
trying. Now come on past the house. Easy! This is the hardest part of
it."

They slipped by. However, Frank uttered a suppressed exclamation as soon
as they had done so. Before them, on the right of the road was a field
easily two or three times as large as the ordinary French field. As a
rule the land in France is split up into very small sections, closely
cultivated. But here was a cleared field as large as those commonly seen
in England or America, with no fences for perhaps a quarter of a mile in
any direction. Henri turned to look back at the inn.

"They're still signalling from there--and look! There are two lights
now, instead of one, above!"

These lights were still some distance away. Frank studied them. Then he
led the way into the field.

"I thought so!" he said, with suppressed triumph in his voice. "Do you
see those barrels over there toward the inn? There's petrol in those--or
I'll eat my shirt!"

"And if there is?" said Henri. "What then?"

"Can't you guess? What do you suppose those lights mean?"

"Aeroplanes?"

"Never! They wouldn't flash that way. They'd have to be in a different
position entirely. No. Dirigibles!"

"Zeppelins?"

"Perhaps. Perhaps Parsevals or Schutte-Lanz airships. I think Parsevals,
for they need gasoline. And Zeppelins could fly from Brussels or Liege,
almost from Cologne--oh, I have it! That's why they need petrol!"

"Why?"

"They haven't flown over Belgium at all! They are from the sea!"

"Oh--so that they could come secretly, and not be seen as they passed
over Belgium?"

"Yes. If they flew over Belgium they would have to cross some territory
that the Germans do not hold, and word would go to Antwerp and from
there to the army here. Now quickly! They will be here soon. They are
coming nearer every minute."

They went to the barrels as fast as they dared. There was nearly a score
of them, all close together. Each had a tap, and it was proof enough
that they contained petrol to open the tap of one. The smell identified
them beyond any doubt whatever.

"Come on, and help me dig a hole," said Frank. He dropped to his knees,
and began scooping out the soft earth with his hands. Henri fell to with
a will, though he was sadly puzzled. But when the hole had been dug to a
depth of perhaps two feet, and Frank began to hollow out a trench toward
the barrels he began to understand. And as soon as he did, he worked as
hard as F