I was sailing in the South Pacific (in the ship "California,") in lat. 24° 20´ south, lon. 125° 6´ west. We were steering south, with the wind north, the sky clear, and the ship going about two knots through the water. At 1, P.M., the officer of the deck reported to me that there were breakers ahead, and on the port bow. I went on deck, and saw what appeared to be an extensive field of breakers, and also a low island or sand bank, thirty feet high, and three miles long, without trees or verdure, and with shoals, on which the sea broke, extending five miles from it to the north and west. The island bore south-east, eight miles distant, and the nearest breakers were two and one half or three miles distant from the vessel. The mate went aloft with me to the mizzen-topsail yard, and with my marine glass we took a good look, and were both entirely convinced that what we saw were genuine breakers. The sea was very smooth and we could see the swell rolling towards us, then cresting, and spreading thin sheets of foam upon the water. The island also appeared very distinct as seen through the glass. I went down on deck with the intention of altering the ship's course, but deciding to run a little nearer to the breakers, I went up to the fore-topsail yard to watch them and steer the ship past them. I soon noticed that they changed their position somewhat, that the ship drew no nearer to them, and that there was a perfect calm where they prevailed. Finally I found the whole appearance was an optical delusion, caused by the sun shining upon the glassy swell of the sea, and a peculiar state of atmospheric refraction. I kept the ship on her course, and sailed through the spot where the first breakers appeared, finding blue water there, but still observing the breakers in the calm spots at varying distances for the next three hours, until 4, P.M., when the breeze freshened at the west, and the illusion was dispelled. The island vanished after being in sight for an hour, and I presume was caused by the looming of the swell of the sea in the horizon. The whole ship's company were deceived by this remarkable appearance, and if circumstances had not favored my prolonged inspection of it, I should certainly have made a report which would have added another to the list of doubtful dangers, which are combined puzzles and terrors to navigators.