History of the Peloponnesian War

But the Peloponnesians became aware of this, and threw into the breach clay packed in reedmats that it might not filter through like the loose earth and be carried away.

But the besieged, thwarted in this direction, gave up that plan and dug a mine from the town, and, guessing when they had got beneath the mound, once more began to draw away the earth to their side, this time from underneath; and for a long time they worked unnoticed by those outside, so that in spite of what they heaped on these made less progress, because their mound, as it was sapped from below, constantly kept settling down into the hollow space.