Then came the frightful explosion of the "Numancia's" bow-torpedo, striking the ill-fated frigate; and then the crushing and splintering of timbers under the fearful stroke of the ram. Five minutes afterwards the Spanish war-ship was alone. Slowly the "Franklin" sank--her lofty mast-heads going under with the stars and stripes still proudly floating from them. The "Numancia" lowered her boats to pick up survivors. They returned with one officer and two seamen--all that remained of the crew of nearly one thousand souls. The American flag ship had been sunk by a fourth-rate European ironclad--the first practical proof of the miserably short-sighted policy of a nation of fifty millions of inhabitants, with an enormous coast line and innumerable ports to be protected, relying for its safety upon a navy the fifty-five available vessels of which are too slow to run away, and too lightly armed and too weakly built to defend themselves. The "Numancia" hoisted her boats and stood to the westward. Shortly afterward she exchanged signals with the "Zaragoza," "Arapiles" and "Vittoria." The war-vessels drew together, the transports came alongside of them, and fresh supplies of coal and provisions were delivered. Then the transports headed to the south, and the men-of-war laid their course for New York. III. THE METROPOLIS BELEAGUERED. Three ships of the Spanish squadron named were armed with Armstrong guns. Their combined batteries aggregated eight cannon of eighteen tons four of twelve tons, eleven of nine tons, and twenty-eight of seven tons. The "Zaragoza" carried twenty guns of another pattern, ranging in calibre from eleven to seven and three-fourths inches. The total number of cannon which would thus be brought to bear upon New York and its suburbs was seventy-one. The shot of the Armstrong guns above named vary in weight from four hundred to one hundred and fifteen pounds. If the entire number of guns should each deliver one shot, the total amount of iron projected would exceed six tons in weight. The arrival of the Spanish vessels was not known until dawn of the morning of April 11th. Then they were descried on the horizon by the watchers at Sandy Hook. At first sight it was supposed that they had encountered heavy weather and lost their light spars; but, as they approached nearer, it was seen that each ship had sent down all her upper rigging, and had housed topmasts. There was no mistaking what this meant. It was the stripping for battle. It was also noticed that the ships steamed very slowly in single file; that from the bows of each projected a fork-like contrivance, and that in advance of the leader were several steam-launches, between which, and crossing the path of the large vessel, extended hawsers which dipped into the water. Evidently the new-comers had a wholesome dread of torpedoes, and hence the use of bow torpedo-catchers and the dragging-ropes. No flag of any sort was exhibited.