The upper deck of the _Stromboli_ had a dozen plate-glass openings, through which a number of powerful electric lights illuminated the depths of the ocean, and enabled the men in charge of the machinery to direct with accuracy the work of fastening the torpedoes. If it had been necessary, men in submarine armor, fastened to steel arms projected from the _Stromboli_, and supplied with air through rubber tubes, could have been placed at work on the bottom of the _Esmeralda_, and maintained there for hours, even while she was coursing through the seas. But it was not necessary to invoke this process, for, by the aid of the ordinary machinery of the _Stromboli_, the three great shells were fastened in twenty minutes’ time, and the _Esmeralda_ was proceeding on her journey with fifteen hundred pounds of potentite fastened to her keel. The officers and crew of the _Esmeralda_ all subsequently testified that this work was performed noiselessly and without jar, or any evidence that it was going forward. But had they possessed all knowledge, they could not have prevented it. No rate of speed possible to the doomed vessel would have enabled her to outrun the speedier submarine torpedo boat, and no machinery or appliance could have reached her under the keel of the _Esmeralda_, or prevented her work, and once the potentite shells were in place, it was beyond the power of man to remove them, and no human skill could prevent the explosion taking place at the appointed time. The introduction of this deadly force into naval warfare was not intended to be unaccompanied with some merciful provisions for preventing unnecessary destruction of human life, and a code of signals had been prepared for all naval powers, to be used whenever a vessel was to be destroyed. The _Stromboli_, having performed her duty, glided from under the keel of the _Esmeralda_, and, at a distance of a few hundred yards, shot up a signal pipe above the surface of the ocean, and with her electric whistle shrieked through it a succession of signals that were heard by the multitude upon the fleet a mile away. “Submarine torpedo boat has been underneath your keel,” said one short shriek, and one more prolonged. “Fifteen hundred pounds of the most powerful explosive known to science are fastened to you,” said fifteen short shrieks. “Make ready to count your minutes of life,” said one long and two short shrieks. “In thirty-six minutes your ship will be hurled in fragments into the air,” said thirty-six short shrieks. “Leave your ship to her inevitable fate. Launch your boats and save your lives. Your enemy will pick you up and receive your honorable surrender,” said one shriek, continued for five minutes.