Of late years immense improvements have taken place, both in the make of the machines employed, and in the methods of working them. Past soundings were few and unsystematic; whereas now they are many and by rule. Thermometers have been made which bring up from the bottom of the sea reports of the prevailing heat or cold, moving unaffected through warm or cold layers between. Specimens of the materials which lie on the ocean-floor have been brought to light, and analysed. Living creatures in great numbers have been hauled from their own domains, examined and classified.
All this means progress. And though, no doubt, fifty or a hundred years hence, that which we now know will be looked upon as the barest A B C of the science, still our knowledge is growing year by year. The Under-Ocean is no longer a vague fairy-land of possible mermaids, or a waste region of death.
A region of death in one sense it is and must be. All living creatures that die in the sea, unless devoured by other creatures, sink to the bottom, there to find a tomb. Covered at first by a vast winding-sheet of water, they may be slowly buried under the shifting mud and sand. But in this sense the whole Crust of Earth may be called one vast sepulchre, wherein all animals that die are entombed.
People are slow to realise how modern is our knowledge of ocean-depths. About three hundred years ago a famous navigator made the first sounding which went below two hundred fathoms—that is, about one hundred feet deeper than the height of Beachy Head from the shore. He at once decided that, by a happy chance, he had alighted upon the uttermost depth in the ocean.
To him it was an awe-inspiring profundity. Yet, when viewed beside such abysses as have been recently discovered, depths of five and six miles, his little “deep” was as a saucer beside a lake.
It is not easy to picture to ourselves the changeless calm of those abysses—those five or six miles of under-water, with nothing from sea-level to sea-floor to break the dead monotony.
Throughout such regions storms, no matter how terrible, have no power. Winds cannot reach them. When Ocean’s surface is lashed by a hurricane into wild commotion, that commotion is superficial. It means a furious stirring and flurry of upper layers; and it means no more.
If at the height of some fierce tornado, a sailor could leave his tossing straining ship, and could dive far into the sea, keeping breath and sense and life, he would soon quit the turmoil, and would find himself in a scene of deep repose. Strange to say, the idea of submarine ships actually doing this has been mooted, as one of the new projects in the beginning of the Twentieth Century.
Wave-motion does not descend much below the surface. It is believed that the depth of water affected by a wave is usually about equal to the space which divides crest from crest. So, if we are looking at little ripples, flowing one after another, with crests perhaps one foot apart, we may suppose that the water is disturbed by those ripples to a depth of about one foot. Or, if we are watching larger waves, with crests twenty feet apart, we may suppose the disturbance to reach down to a depth of some twenty feet. And if our gaze is fixed on dignified Atlantic rollers, with crests six or eight hundred feet apart, we may suppose that the sea is affected to a depth of six or eight hundred feet—less and less affected the deeper we go down.
Six or eight hundred feet, compared with six miles, are hardly more than a man’s skin compared with his body. And beyond the shallow depths where wind and wave have sway, we come to a region of profound calm.