it was in operation.

We then withdrew our camp farther away down the river, to a point where
the conformation of the country made a repetition of this attack
impossible. A sort of guerrilla warfare now began in the mountains. Our
scouting parties frequently met Tao's men, and many encounters, swiftly
fatal to one side or the other, took place. But all the time we were able,
at intervals, to rake the valley with our fire for brief periods.

Mercer constantly was evolving plans of the utmost daring, most of them
indeed amounting practically to suicide for those undertaking them. But I
held him back. Our present tactics were dangerous enough, although after
the first few fatalities we succeeded in protecting our men, even though
our projectors were invariably destroyed.

One of Mercer's plans we tried with some success. There were some places
in the light-barrage that were much less high than others. We devised a
smaller rocket that could be fired from the platforms. Mercer took it up
some twenty thousand feet, and sent several rockets over the light, which
we hoped dropped into the city.

A month went by in this way. We were in constant communication by water
with the Great City, receiving supplies and reenforcements of men and
armament. And then gradually the situation changed. Over a period of
several days our hand-to-hand encounters with the enemy grew less
frequent. Finally two or three days went by without one of them taking
place.

We became bolder and prepared to establish several projectors at different
points for simultaneous fire at a given signal. The light-barrage in the
valley remained unchanged, although now its beams held steady instead of
sometimes swinging to and fro. We dislodged one of its projectors with a
rocket, making a hole in the barrage, which this time was not repaired.
And then, to our amazement, the lights one by one began to die away. We
ceased operations, waiting. Within half a day they had all vanished, like
lights which had flickered and burned out.

Mercer, unthinking, was all for an instant attack. We could indeed have
swept the valley now without difficulty; but there were thousands of
people in the city--non-combatants, women and children--and to murder them
to no purpose was not the sort of warfare we cared to make.

It seemed probable that Tao had evacuated his position. The valley beyond
the city led up into the mountains toward the Dark City, almost on the
borderland of th