Early on the night of the 4th of April, the prince of Parma and his army were amazed by the spectacle of three huge masses of flame floating down the river, accompanied by numerous lesser appearances of a similar kind, and bearing directly against the prodigious barrier, which had cost months of labor to him and his troops, and immense sums of money to the state.  The whole surface of the Scheldt presented one sheet of fire; the country all round was as visible as at noon; the flags, the arms of the soldiers, and every object on the bridge, in the fleet, or the forts, stood out clearly to view; and the pitchy darkness of the sky gave increased effect to the marked distinctness of all.  Astonishment was soon succeeded by consternation, when one of the three machines burst with a terrific noise before they reached their intended mark, but time enough to offer a sample of their nature.  The prince of Parma, with numerous officers and soldiers rushed to the bridge, to witness the effects of this explosion; and just then a second and still larger fire-ship, having burst through the flying bridge of boats, struck against one of the estoccades.  Alexander, unmindful of danger, used every exertion of his authority to stimulate the sailors in their attempts to clear away the monstrous machine which threatened destruction to all within its reach.  Happily for him, an ensign who was near, forgetting in his general’s peril all rules of discipline and forms of ceremony, actually forced him from the estoccade.  He had not put his foot on the river bank when the machine blew up.  The effects were such as really baffle description.  The bridge was burst through; the estoccade was shattered almost to atoms, and, with all that it supported—­men, cannon, and the huge machinery employed in the various works—­dispersed in the air.  The cruel marquis of Roubais, many other officers, and eight hundred soldiers, perished in all varieties of death—­by flood, or flame, or the horrid wounds from the missiles with which the terrible machine was overcharged.  Fragments of bodies and limbs were flung far and wide; and many gallant soldiers were destroyed, without a vestige of the human form being left to prove that they had ever existed.  The river, forced from its bed at either side, rushed into the forts and drowned numbers of their garrisons; while the ground far beyond shook as in an earthquake.  The prince was struck down by a beam, and lay for some time senseless, together with two generals, Delvasto and Gajitani, both more seriously wounded than he; and many of the soldiers were burned and mutilated in the most frightful manner.  Alexander soon recovered; and by his presence of mind, humanity, and resolution, he endeavored with incredible quickness to repair the mischief, and raised the confidence of his army as high as ever.  Had the Zealand fleet come in time to the spot, the whole plan might have been crowned with success; but by some want of concert, or accidental delay, it did not appear; and consequently the beleaguered town received no relief.