-throated sound of a heavy gun. It made them jump; and the entire
village seemed to become aroused at once, as people began to run this
way and that, chattering like magpies, some of their faces turning white
with apprehension of what was to come.

They had heard of the fate of Louvain, and dreaded the hour when the
German army should come sweeping with irresistible force across that
section of the country.

Quick on the heels of that opening gun came other sounds--the long roll
of rifle firing in volleys, and the faint cheers of charging men. The
boys even fancied they could hear amidst all the confusion the loud
singing that was said to mark the advance of the German legions as they
went into battle chanting the "Watch on the Rhine." Rob could well
believe it, for he knew singing was to the Teuton mind what the bagpipes
meant to Scotch Highlanders, or cheers to American boys in khaki.

It was evident that the gallant little Belgian army, determined to
resist to the uttermost the passage of the Germans across their
territory in the direction of Antwerp and Ghent, had again given battle
to overwhelming numbers.

Of course the boys had rushed out of the inn and immediately sought the
best position from which they could see something of what was going on.
Many of the villagers were clustered there, gazing with deepest concern
at the section where the smoke of battle was beginning to spread like a
pall over the country.

"Oh! what is that up there, and heading this way?" Tubby suddenly
exclaimed.

No sooner had Rob turned his gaze aloft than he was able to give the
desired information.

"That is one of the famous German Zeppelins, hovering over the
battlefield," he told Tubby.

CHAPTER XVI.

THE BATTLE FOR THE TRENCHES.

By this time everyone was gazing in mixed wonder and awe at the strange
dirigible balloon, speeding in great circles far up toward the clouds.

Rob and his comrades had read more or less about these monster airships
which the German Count had invented, and which were expected to play a
prominent part in this world war. They had even hoped that before they
left Belgium they might be given an opportunity to see one of the fleet
monsters, which were said to be able to carry dozens of men, as well as
tons of explosives, incredible distances.

In Antwerp there had been considerable talk concerning the possibility
of these Zeppelins making a concerted attack on the city, and forcing
its s