Suddenly there was a terrific sound like an explosion, then a crash that shook the earth for miles around, and made Gysbert's little boat rock on the waves till it all but over-turned completely. When the boy recovered himself enough to realize what had happened, it did not take him long to explain the dreadful sounds. Undermined by the stream so long secretly eating at its base, the whole wall of Leyden between the Cow Gate and the Tower of Burgundy had suddenly fallen in utter ruins!
Gysbert rowed away frantically from the scene of destruction. He had not, for the moment, the slightest idea what direction he was taking, but his mind was actively at work. The wall of Leyden had fallen in for the space of nearly a quarter of a mile! If the Spaniards had the faintest suspicion of this, he reasoned, they would flock immediately to the scene, and make an easy and terrible entrance. There was no defending the breach from the _inside_, for the brave, but hunger-enfeebled corps of John Van der Does would be as nothing before the fierce thousands of the Spanish army. To his mind there remained but one course,--he must in some way get word to Admiral Boisot and his Sea Beggars, and let them make an entrance into the city before the Spaniards got wind of the disaster.
With this end in view he looked about him, ascertained as nearly as he could the position of the fleet, and commenced to row steadily in that direction. As he drew near the Fortress of Lammen, however, he became aware that something very strange was taking place. Wonderingly he shipped his oars and turned about to watch the curious sight. Myriads of tiny lights twinkled across the dark waste of waters. There was almost no sound, but only a vague impression that something mysterious was happening. After a time the lights formed themselves into a long procession which seemed to flit steadily across the one remaining causeway that led to the Hague.
The boy sat breathless, eager, marvelling at this apparently never-ending procession of lights, twinkling in single file over what seemed the very face of the water. For a time he could find no explanation for this singular spectacle, till all at once the truth flashed on him. The Spaniards were retreating! Under cover of darkness, they were silently sneaking away, fleeing panic-stricken from the unknown terror of that hideous sound in the night,--fleeing like cowards at the very moment when fortune had rendered their entrance to the coveted city as easy as stepping over a log!