Those are pearls that were his eyes:
Nothing of him that doth fade
But doth suffer a sea-change
Into something rich and strange.
The transfiguration of familiar objects is indeed curious and wonderful. The hulk, once gaudy with paint and gilding, has come under the skill of the lapidary and sea-artist. It is crusted with emerald and flossy mosses, and glimmers with diamond, jacinth, ruby, topaz, sapphire and gold. Every jewel-shape in leaf, spore, coral or plume, lying on a greenish crystalline ground, is fringed with a soft radiance of silver fire, and every point is tipped in minute ciliate flames of faint steely purple. It is spotted with soft velvety black wherever a shadow falls, that mingles and varies the wonderful display of color. It is brilliant, vivid, changeable with the interferences of light from the fluctuating surface above, which transmogrifies everything—touches the coarsest objects with its pencil, and they become radiant and spiritual. A pile of brick, dumped carelessly on the deck, has become a huge hill of crystal jewelry, lively with brilliant prismatic radiance. Where the light falls on the steps of the staircase it shows a ladder of silver crusted with emeralds. The round-house, spars, masts, every spot where a peak or angle catches the light, have flushed into liquid, jeweled beauty; and each point, a prism and mirror, catches, multiplies and reflects the other splendor. A rainbow, a fleecy mist over the lake, made prismal by the sunlight, a bunch of sub-aqueous moss, a soap-bubble, are all examples in our daily experience of that transforming power of water in the display of color. The prevailing tone is that soft, golden effulgence which, like the grace of a cheerful and loving heart, blends all into one harmonious whole.
But observation warns the spectator of the delusive character of all that splendor of color. He lifts a box from the ooze: he appears to have uncorked the world. The hold is a bottomless chasm. Every indentation, every acclivity that casts a shadow, gives the impression of that soundless depth. The bottom of the sea seems loopholed with cavities that pierce the solid globe and the dark abysses of space beyond. The diver is surrounded by pitfalls, real and imaginary. There is no graduation. The shallow concave of a hand-basin is as the shadow of the bottomless well.
If the exploration takes place in the delta of a great river, the light is affected by the various densities of the double refracting media. At the proper depth one can see clearly the line where these two meet, clean cut and as sharply defined as the bottom of a green glass tumbler through the pure water it contains. The salt brine or gelatinous sea-water sinks weighted to the bottom, and over it flows the fresh river-water. If the latter is darkened with sediment, it obscures the silent depths with a heavy, gloomy cloud. In seasons of freshet this becomes a total darkness.
But even on a bright, sunshiny day, under clear water, the shadow of any object in the sea is unlike any shade in the upper atmosphere. It draws a black curtain over everything under it, completely obscuring it. Nor is this peculiarity lost when the explorer enters the shadow; but, as one looking into a tunnel from without can see nothing therein, though the open country beyond is plainly visible, so, standing in that submarine shadow, all around is dark, though beyond the sable curtain of the shadow the view is clear. Apply this optical fact to the ghastly story of a diver's alleged experience in the cabin of a sunken ship. It is narrated that there was revealed to his appalled sight the spectacle of the drowned passengers in various attitudes of alarm or devotion when the dreadful suffocation came. The story is told with great effect and power, but unless a voltaic lantern is included in the stage furniture, the ghastly tableaux must sink into the limbo of incredibilities.
The cabin of a sunken vessel is dark beyond any supernal conception of darkness. Even a cabin window does not alter this law, though it may be itself visible, with objects on its surface, as in a child's magic-lantern. As the rays of light pass through an object flatwise, like the blade of a knife through the leaves of a book, and may be admitted through another of like character in the plane of the first, so a ray of light can penetrate with deflection through air and water. But becoming polarized, the interposition of a third medium ordinarily transparent will stop it altogether. Hence the plate-glass window under water admits no light into the interior of a cabin. The distrust of sight grows with the diver's experience. The eye brings its habit of estimating proportion and distance from an attenuated atmosphere into another and denser medium, and the seer is continually deceived by the change. He hesitates, halts, and is observant of the pitfalls about him. A gang-plank slightly above the surface of the deck is bordered, where its shadow falls, by dismal trenches. There is a range of hills crossing the deck before him. As he approaches he estimates the difficulty of the ascent. At its apparent foot he reaches to clamber the steep sides, and the sierra is still a step beyond his reach. Drawing still nearer, he prepares to crawl up; his hand touches the top; it is less than shoulder-high.
But perhaps the strongest illustration of the differing densities of these two media is furnished by an attempt to drive a nail under water. By an absolute law such an effort, if guided by sight independent of calculation, must fail. Habit and experience, tested in atmospheric light, will control the muscles, and direct the blow at the very point where the nail-head is not. For this reason the ingenious expedient of a voltaic lantern under water has proved to be impracticable. It is not the light alone which is wanted, but that sweet familiar atmosphere through which we are habituated to look. The submarine diver learns to rely wholly on the truer sense of touch, and guided by that he engages in tasks requiring labor and skill with the easy assurance of a blind man in the crowded street.