It is the general impression, that if a water-spout touches an object, or is struck, its form is broken, and the water descends; but this is not always the case. I was standing one day upon the sea-wall of Fort Jefferson, on the island of Tortugas, Florida reef, when I perceived a lofty water-spout, a mile to the east, headed directly for the fort, as I thought. In a few moments it struck Long Key, a narrow island a quarter of a mile away; passing over perhaps one hundred and fifty feet of it, striking a small schooner which had been hauled upon the beach, twisting it around, and then continuing its course with great rapidity. It now turned a little to the north; and, seeing that in all probability it would not strike the fort, I awaited its coming. Never shall I forget the awful grandeur of the sight, as the watery monster, seemingly several thousand feet in height, reached the shoal. For some reason which I cannot explain, the central portion was invisible, but the upper part was distinctly seen, and appeared to be nearly over my head; and its proximity may be imagined from the fact that the drops from it seemed like a heavy rain. The entire spout was bent like a bow by the wind, and was moving along with great rapidity. I could not keep up with it, though running at utmost speed as it passed. Its progress was accompanied by a loud roar, and a hissing, splashing sound, while great masses of foam were thrown up before and behind. In its wake followed numbers of gulls, feeding upon the small fishes killed by the rush of waters; and where it crossed the shoal, in perhaps eight feet of water, quite a trench was scooped out. Imagine such a column at night coursing over the ocean; its entire shape outlined against the darkness in phosphorescent light (Plate XXV.), and an idea may be gained of the magnificent spectacles which, on rare occasions, are produced by some of the simplest of plants,--the diatoms,[45] whose nuclei are luminous. The southern oceans, in certain places, often swarm with these minute light-givers, and when borne aloft in the spout, they tend to produce one of the most remarkable and striking scenes possible to imagine. In color these luminous columns are yellow, of different shades, according to the numbers of diatoms present. The naturalists of the “Challenger” found that _P. pseudo-noctiluca_ was always present, and often existed at the surface in vast numbers, in the tropics and subtropical regions where the temperature was over sixty-eight or seventy degrees; and the most beautiful exhibitions seen during the cruise were due to these little forms. They have been observed in the Bay of Funchal all the year round. The light was equally brilliant in each species; and in each, when disturbed several times in succession, the phosphorescence perceptibly diminished, and finally disappeared: but after an hour’s rest, it re-appeared as brilliant as before.