"'Now, then,' said he, 'you know a mine when you see one, so will you please stand by the conning-tower look-out; I'll keep the vessel on her course by means of the periscope.' "So saying he descended a short iron ladder and took his stand before a small table coated with highly polished silver. This mirror reflected an erect, right image, or, in other words, a faithful reproduction of the horizon as seen from the surface. "We were running at six knots, so that taking into consideration the strength of the ebb, our rate over the ground was a bare three knots, thus allowing an ample margin to bring up should we sight an obstruction." "How far could you see ahead?" "About 100ft., for the water was fairly translucent in the bright sunshine. Had it been dark we could have used a powerful searchlight. "Suddenly I caught sight of a barrel-shaped object straining at its sinker and cable like a gigantic long-stalked mushroom. Palmer was instantly at my side, having ordered the motors to be eased down. The principle on which the torpedoes are fired is similar to that by which the guns are discharged on board this ship. I saw the slender, fish-shaped weapon leave the tube and glide towards the mark, but the target being a small one, and oscillating into the bargain, the torpedo missed it by a foot. "The second shot was successful, and although I did not hear the detonation, the shock was sufficient to make the submarine lurch violently. "This operation was repeated till we found ourselves right inside the harbour, the wharves and the shore being crowded with people attracted by the unwonted spectacle of the presence of a mysterious battleship in the offing." "Then it's certain that all the mines have been destroyed?" "All in the channel, at all events, for we could see the outlines of the shoal on either hand, and not a trace of a mine remained. But there's the engine-room telegraph; we're getting under way once more, so let's go on deck." On gaining the fo'c'sle the two chums found the Chilian skipper shaking with apprehension and anxiety. He had been led for'ard and was conning the ship under the charge of Lieutenant Sinclair, who was an expert Spanish linguist. The lieutenant communicated the pilot's directions to the quartermaster in the conning-tower, who in turn held the _Olive Branch_ on her course at a steady five knots. Even then the depth on the bar was so little that for some considerable distance the ship's remaining propellers churned up columns of liquid mud. Cleared for action she slowly approached the harbour, but, as anticipated, there was no sign of resistance from the forts. On the contrary they respectfully dipped their flags, a compliment that the _Olive Branch_ returned by lowering her green and white ensign.