The six men hurried to the tower.

A long loophole had been fashioned in the thick wall on a downward slant, so that a marksman might command anyone who crept forward to fire the fort.

Against this loophole Luffe leaned his ear.
"Do you hear anything, sir ?" asked a subaltern of the Sappers who was attached to the force.
"Hush!" said Luffe.
He listened, and he heard quite clearly underneath the ground below him the dull shock of a pickaxe.

The noise came almost from beneath his feet; so near the mine had been already driven to the walls.

The strokes fell with the regularity of the ticking of a clock.