On the 8th of June, being then in latitude 00° 30′ south, and longitude 27° 5′ west, having fine weather and a fresh south-easterly trade wind, and range of the thermometer being from 78° to 84°, late at night the mate of the watch came and called me to witness a very unusual appearance in the water, which he, on first seeing, considered to be breakers. On arriving upon the deck, this was found to be a very broad and extensive sheet of phosphorescence, extending in a direction from east to west as far as the eye could reach; the luminosity was confined to the range of animals in this shoal, for there was no similar light in any other direction. I immediately cast the towing net over the stern of the ship as we approached nearer the luminous streak, to ascertain the cause of this extraordinary and so limited a phenomenon. The ship soon cleaved through the brilliant mass, from which, by the disturbance, strong flashes of light were emitted; and the shoal (judging from the time the vessel took in passing through the mass) may have been a mile in breadth: the passage of the vessel through them, increased the light around to a far stronger degree, illuminating the ship. On taking in the towing net, it was found half filled with _pyrosoma_, (atlanticum?) which shone with a beautiful pale greenish light, and there was also a few small fish in the net at the same time; after the mass had been passed through, the light was still seen astern until it became invisible in the distance, and the whole of the ocean then became hidden in darkness as before this took place. The scene was as novel as it was beautiful and interesting, more so from having ascertained, by capturing the luminous animals, the cause of the phenomenon.