At about every hundred yards Dymock had to cross one of the numerous deep channels that intersect the sands, till further walking was impossible at the edge of the main channel. Here he was within a hundred yards of the northernmost of the enemy's batteries. He could distinguish the sentries slowly pacing to and fro, their figures silhouetted against the glare of the camp-fires.
As noiselessly as a water-rat the intrepid messenger glided into the swift-flowing stream, and, swimming with a powerful breast-stroke, soon began to visibly lessen the distance 'twixt him and his goal. Now the outermost battery was left behind. Should the alarm be raised his retreat would be cut off, for at the faintest suspicion, armed boats, provided with bright lanterns, would push off and patrol the narrow channel.
Against the loom of the lights he could see a low-lying dark mass stretched across the stream from bank to bank. It was the boom. Fifty strokes brought him up to the obstruction, but in vain his fingers sought to find a hold upon the slimy weed-covered baulks of timber. The suction of the current swept his legs beneath the woodwork, and only by an effort was he able to kick himself clear of the floating mass.
"Then if I can't climb I must needs dive under it," muttered Dymock, for he felt that in the struggle his strength was failing him, and unless something was done he would be pinned by the dark torrent against the side of the boom.
Taking a deep breath he swam downwards. Dark as was the night the utter blackness of the water was still more so. He was groping blindly beneath the waves.
Already he had lost all sense of direction. He realised that he must keep to the required depth and trust to the current to sweep him beneath the floating mass of timber. He felt that he must rise—yet dared not. His breath was well-nigh exhausted.
Suddenly he felt his body come in contact with a sharp pointed object. It was one of the stakes fixed in the bed of the river. Then the terrible thought assailed him—was the space enough betwixt the tips of the stakes and the bottom of the boom?
Rising slightly he felt the tide sweep him past the obstruction. The iron point scraped his flesh, but in his anxiety and with the numbness of his body the pain was not worth noticing. It was mental not bodily torment that he felt. Even as he rose his head struck a barnacle-covered baulk, but with barely six inches to spare he was swept betwixt his Scylla and Charybdis: then up and up he swam till his head emerged above the surface and he drank in pure night air.
Turning on his back Dymock floated, breathing deeply and resting his tired limbs. The worst of his journey was now over, thought he; with the tide the passage betwixt the remaining batteries was merely a question of time. Now he could discern the low ramparts, the shattered houses, and the battered cathedral tower of the beleaguered city. With renewed energy, fired by the sense of duty, he once more struck out, though his strokes were more feeble than of yore.
But Dymock's assurances were short-lived. Rowing straight in his direction was a boat—not one of the besiege's patrol craft, but a small skiff manned by two rowers, who were taking a French officer across the river.