It was thus that, either by overloading her reservoirs or by descending obliquely by means of her inclined planes, the Nautilus successively attained the depth of three, four, five, seven, nine, and ten thousand yards, and the definite result of this experience was that the sea preserved an average temperature of four degrees and a half at a depth of five thousand fathoms under all latitudes.

On the 16th of January, the Nautilus seemed becalmed only a few yards beneath the surface of the waves. Her electric apparatus remained inactive and her motionless screw left her to drift at the mercy of the currents. I supposed that the crew was occupied with interior repairs, rendered necessary by the violence of the mechanical movements of the machine.

My companions and I then witnessed a curious spectacle. The hatches of the saloon were open, and, as the beacon light of the Nautilus was not in action, a dim obscurity reigned in the midst of the waters. I observed the state of the sea, under these conditions, and the largest fish appeared to me no more than scarcely defined shadows, when the Nautilus found herself suddenly transported into full light. I thought at first that the beacon had been lighted, and was casting its electric radiance into the liquid mass. I was mistaken, and after a rapid survey perceived my error.

The Nautilus floated in the midst of a phosphorescent bed which, in this obscurity, became quite dazzling. It was produced by myriads of luminous animalculae, whose brilliancy was increased as they glided over the metallic hull of the vessel. I was surprised by lightning in the midst of these luminous sheets, as though they bad been rivulets of lead melted in an ardent furnace or metallic masses brought to a white heat, so that, by force of contrast, certain portions of light appeared to cast a shade in the midst of the general ignition, from which all shade seemed banished. No; this was not the calm irradiation of our ordinary lightning. There was unusual life and vigour: this was truly living light!

In reality, it was an infinite agglomeration of coloured infusoria, of veritable globules of jelly, provided with a threadlike tentacle, and of which as many as twenty-five thousand have been counted in less than two cubic half-inches of water.

During several hours the Nautilus floated in these brilliant waves, and our admiration increased as we watched the marine monsters disporting themselves like salamanders. I saw there in the midst of this fire that burns not the swift and elegant porpoise (the indefatigable clown of the ocean), and some swordfish ten feet long, those prophetic heralds of the hurricane whose formidable sword would now and then strike the glass of the saloon. Then appeared the smaller fish, the balista, the leaping mackerel, wolf-thorn-tails, and a hundred others which striped the luminous atmosphere as they swam. This dazzling spectacle was enchanting! Perhaps some atmospheric condition increased the intensity of this phenomenon. Perhaps some storm agitated the surface of the waves. But at this depth of some yards, the Nautilus was unmoved by its fury and reposed peacefully in still water.