These tunnelling operations would have been infinitely more tedious and more arduous had not an elaborate system of subterranean passages already been provided by Major Wardlaw. Various cunningly devised galleries bad been secretly cut in the hill in order to furnish the garrison of the Fort (on the assumption that the garrison would be English and acting on the defensive), with the means of taking an attacking force in the rear, and of laying mines for the destruction of any besiegers. But the tables had been turned, though how far, if at all, the invaders were aware of these hidden avenues and the method by which they could be made available, remained a matter of doubt and anxious speculation to the British Staff. Meanwhile, hour after hour, deep in the heart of the hill, the sappers sweated at their work. Nearer and nearer they approached to the spot at which a mine, if exploded, might be expected to shatter at least a section of the Fort, and open a way for British bayonets to enter. A few more yards and the vital point would be reached. Then, suddenly, the sapper who was wielding a pickaxe in advance of all the rest paused in his work, listening intently. He raised his hand excitedly, and the officer in command of the party instantly crept forward, and with an imperious gesture stopped the work. The sappers, their faces shining in the lantern light, at first wondered what it meant. But soon enough they heard and understood. Faintly, as through a massive wall, there came to their ears the fateful sound of tapping--the click, click, click of other pickaxes. It came from below the tunnel they themselves were cutting. One thing, and only one, could explain the sound. The invaders had found out, or someone had betrayed to them, one of the secret tunnels of the hill. The sappers, pale as death, gazed in each other's faces. In a flash they realised the awful jeopardy in which they stood. The invaders were counter-mining at a lower stratum! beneath their very feet. At any moment--while a breath was drawn or glances were exchanged--they might explode their mine! There was an awesome pause, then the officer gave a sharp, half-whispered order. Instantly, boldly, the picks were at their work again. It was a desperate race for time--here in this cramped tunnel--in the smothering depths of mother earth; and no man's life was worth a moment's purchase. Yet iron self-discipline prevailed. The sappers worked with almost frenzied haste and vigour. After ten minutes of furious, exhausting labour, they were allowed to pause. The chests of the toilers heaved painfully; some of them tried to hold their breath; others shook their heads impatiently, as if to stop the singing in their ears. They wanted to listen, to hear, and know their fate.