It was about six bells in the afternoon watch when, with a sudden darkening of the sky, that came upon us like the gloom of night, it began to rain--a regular tropical deluge, sluicing down upon us in sheets, as though the bottom of a cloud had dropped out; and within less than a minute our decks were more than ankle-deep in warm fresh water, and our scuppers were running full.  The downpour lasted for perhaps a minute and a half, and then ceased as abruptly as though a tap had been turned off, and we heard the shower passing away to the northward of us, leaving us with streaming decks and dripping canvas and rigging.  But, although the rain had come and gone again in the space of a couple of minutes, the darkness intensified rather than otherwise, and presently we heard a muttering of distant thunder away down in the southern quarter, followed, after a while, by a further dash of rain, lasting for a few seconds only.