th what? With
large-caliber shells, perhaps. But still it was only a supposition. A
few days later, however, it was noticed that at a certain point on the
westward edge of that patch of woods there seemed to be a slight
discoloration. This discoloration became more pronounced on later
photographs which were brought in. Every one in the Section
Photographique hazarded a guess as to its cause. At length some one
suggested that it looked as though the leaves of the trees had been
burned. But what burned them? There was only one answer. The fiery
blast from a big gun hidden amid those trees, of course! Acting on
that hypothesis, a score of aviators were sent out with orders to pour
upon the wood a torrent of high explosive. The next few hours must
have been very uncomfortable for the German gun-crew. In any event,
the big piece was hauled out of danger under cover of darkness and the
bombardments of the towns behind the Belgian lines abruptly ceased.

The Allied air service does not confine its observations to the
trenches; it keeps an ever-wakeful eye on all that is in progress in
the regions for many miles behind the front. To illustrate how little
escapes the eye of the camera, the officer in charge of the
Photographic Section showed me a series of photographs which had been
taken of a village at the back of Dixmude, a few days previously, from
a height of more than a mile. The first picture showed an ordinary
Flemish village with its gridiron of streets and buildings. Cutting
diagonally across the picture was a straight white streak which I knew
to be a road leading into the country. At one point on this road were
a number of tiny squares--evidently a row of workmen's cottages. The
commandant handed me a powerful magnifying-glass. "Look very closely
on that road," he said, "and you will see three specks." I saw them.
They were about the size of pin-points.

"Those are three men," he continued. "The man at the right lives in
the first of this row of cottages. The man in the middle lives in the
fourth house in the row. But the man at the left is a farmer, and
lives in this isolated farmhouse out here in the country."

"A very clever guess," I remarked, scepticism showing in my tone, I
fear.

"We do not guess in this business," he replied reprovingly. "We
_know_." And he handed me the next photograph, taken a few seconds
later. There was no doubt about it; the pin-point of a man at the
right had left his two companion