DOWN IN THE DEPTHS OF THE OCEAN.

New Zealand Graphic, Volume XVIII, Issue XIX, 8 May 1897, Page 585

DOWN IN THE DEPTHS OF THE OCEAN.

The temperature at the bottom of the ocean is nearly down to freezing point, and sometimes actually below it. There is a total absence of light, as far as sunlight is concerned, and there is an enormous pressure, reckoned at about one ton to the square inch in every 1,000 fathoms, which is 160 times greater than that of the atmosphere we live in. At 2,500 fathoms the pressure is thirty times more powerful than the steam pressure of a locomotive when drawing a train. As late as 1880 a leading zoologist explained the existence of deep sea animals at sach depths by assuming that their bodies were composed of solids

and liquids of great density, and contained no air. Tbi*, however, is not the case with deep sea fish, which are provided with air-inflated swimming bladders. If one of these fish, in full ehase after its prey, happens to ascend beyond a certain level, its bladder becomes distended with the decreased pressure, and carries it, in spite of all its efforts, still higher in its course In fact, members of this uufortunate class are liable to become victims to the unusual accident of falling upward, and no doubt meet with a violent death soon after leaving their accustomed level and long before their bodies reach the surface in a distorted and unnatural state. Even ground sharks brought up from a depth of no more than 500 fathoms, expire before they gain the surface. The fauna of the deep sea—with a few exceptions hitherto only known as fossils — are new and specially modified forms of families and genera inhabiting shallow waters in modern times, and have been driven down to the depths of the ocean by their more powerful rivals in the battle of life, much as the ancient Britons were compelled to withdraw to the barren and inaccessible fastnesses of Wales. Some of their organs have undergone considerable modificationin correspondence to the changed conditions of their new habitats. Thus down to 900 fathoms their eyes have generally become enlarged, to make the best of the faint light which may possibly penetrate there. After 1,000 fathoms these organs are either still further enlarged or so greatly reduced that in some species they disappear altogether and are replaced by enormously long feelers. The only light at great depths which would enable large eyes to be of any service is the phosphorescence of deep-sea animals. We know that at the surface this light is often very powerful, and Sir Wyville Thomson has recorded one occasion on which the sea at night was a * perfect blaze of phosphorescence, so strong that lights and shadows were thrown on the sails and it was easy to read the smallest print.' It is thought possible by several naturalists that certain portions of the sea bottom may be as brilliantly illuminated by this sort of light as the streets of a European city after sunset. Some deep-sea fish have two parallel rows of small circular phosphorescent organs running along the whole length of their bodies, and as they glide through the dark waters of the profound abysses they must look like model mail ships with rows of shining portholes.