Shortly before daybreak, on the third morning after leaving Port Royal, we found ourselves rapidly drawing into smooth water--so rapidly, indeed, that Pearce, the boatswain, whose watch it was, came down in some alarm and roused me out, fearing that Willoughby, the midshipman who was acting as master, had made a mistake in his reckoning, and that we were about to blunder on to some danger or another.  I was able, however, to set the good man's mind at rest by explaining that we were doubtless drawing in under the lee of the Caycos Bank, and that therefore the water might naturally be expected to smoothen. Nevertheless, feeling that I had had a good night's rest, and understanding from Pearce that day would dawn in less than half-an-hour's time, I turned out and, slipping into my trousers and jacket, went up on deck.  And very glad I was that I had done so, for I was thus enabled to observe a very curious natural phenomenon, which one might knock about in those seas for years without seeing, for the simple reason that the circumstances must be favourable or the phenomenon is not visible.