heir heads by shutting off steam immediately the drone of our
engines made itself heard; but we had spotted them from afar, and
already they were noted for the information of Brass Hats.

The next item of interest was activity at a factory outside a little
town. Black trails of smoke stretched away from the chimneys; and
surely, as we approached a minute ago, a short column of lorries was
passing along a road towards the factory. Yet when we reached the spot
there was no sign of road transport. Nevertheless, I was certain I had
seen some motor vehicles, and I entered the fact in my note-book.
Likewise I took care to locate the factory site on my map, in case it
deserved the honour of a bomb attack later.

Our bus led the way across the huge unwieldy Foret de Charbon, patterned
in rectangular fashion by intersecting roads, and we arrived at
Siegecourt. This is at once a fortress and an industrial town. There are
several railway stations around it, and these added greatly to the
observers' collection of trains and trucks. The Huns below, with
unpleasant memories of former visits from British aircraft, probably
expected to be bombed. They threw up at us a large quantity of
high-explosive shells, but the shots were all wide and we remained
unworried. To judge by the quality of the A.-A. shooting each time I
called there, it seemed likely that half-trained A.-A. gunners were
allowed to cut their active service teeth on us at Siegecourt.

Having squeezed Siegecourt of all movement, we headed for Le Recul. Here
the intricate patchwork of railway kept the observers busy, and six more
trains were bagged. Then, as this was the farthest point east to be
touched, we turned to the left and travelled homeward.

It was soon afterwards that our engine went dud. Instead of a rhythmic
and continuous hum there was at regular intervals a break, caused by one
of the cylinders missing explosion at each turn of the rotary engine.
The rev.-counter showed that the number of revolutions per minute had
fallen off appreciably. Decreased revs. meant less speed, and our only
chance to keep with the others was to lose height continuously. We were
then nearly fifty miles from the lines.

I noticed the gap in the engine's drone as soon as it began. An airman
is accustomed to the full roar of his engine, and it never distracts
his attention, any more than the noise of a waterfall distracts those
who live near it. But if the roar becomes non-continuo