Ferragut continued to pass slowly along the Aquarium between the two rows of vertical tanks,—­stone cases with thick glass that permitted full view of the interior.  The clear and shining walls that received the fire of the sun through their upper part, spread a green reflection over the shadows of the corridors.  As they made the rounds, the visitors took on a livid paleness, as though they were marching through a submarine defile.

The tranquil water within the tanks was scarcely visible.  Behind the thick glass there appeared to exist only a marvelous atmosphere, an air of dreamland in which drifted up and down various floating beings of many colors.  The bubbles of their respiration was the only thing that announced the presence of the liquid.  In the upper part of these aquatic cages, the luminous atmosphere vibrated under a continual spray of transparent dust,—­the sea water with air injected into it that was renewing the conditions of existence for these guests of the Aquarium.

Seeing these revivifying streams, the captain admired the nourishing force of the blue water upon which he had passed almost all his life.

Earth lost its pride when compared with the aquatic immensity.  In the ocean had appeared the first manifestations of life, continuing then its evolutionary cycle over the mountains which had also come up from its depths.  If the earth was the mother of man, the sea was his grandmother.

The number of terrestrial animals is most insignificant compared with the maritime ones.  Upon the earth’s surface (much smaller than the ocean) the beings occupy only the surface of the soil, and an atmospheric canopy of a certain number of meters.  The birds and insects seldom go beyond this in their flights.  In the sea, the animals are dispersed over all its levels, through many miles of depth multiplied by thousands and thousands of longitudinal leagues.  Infinite quantities of creatures, whose number it is impossible to calculate, swim incessantly in all the strata of its waters.  Land is a surface, a plane; the sea is a volume.

The immense aquatic mass, three times more salty than at the beginning of the planet, because of a millennarian evaporation that has diminished the liquid without absorbing its components, retains mixed with its chlorides, copper, nickel, iron, zinc, lead, and even gold, from the metallic veins that planetary upheaval deposits upon the oceanic bottom; compared with this mass, the veins of mountains with their golden sands deposited by the rivers are but insignificant tentacles.

Silver also is dissolved in its waters.  Ferragut knew by certain calculations that with the silver floating in the ocean could be erected pyramids more enormous than those in Egypt.

The men who once had thought of exploiting these mineral riches had given up the visionary idea because the minerals were too diluted and it would be impossible to make use of them.  The oceanic beings know better how to recognize their presence, letting them filter through their bodies for the renovation and coloration of their organs.  The copper accumulates in their blood; the gold and silver are discovered in the texture of the animal-plants; the phosphorus is absorbed by the sponges; the lead and the zinc by species of algae.