OCEAN DEPTHS

Hawera Star, Volume XLVII, 21 April 1928, Page 11

OCEAN DEPTHS

'J'HERE i s a prevalent idea that as

one goes deep down into the oceans the water at those profound depths increases greatly in density and takes on a consistency like treacle as. a result of the great pressure to which it is subjected. As a corollary to this belief - it is often thought that ships and bodies and the like do not sink to the ocean bed, but “find their level” and float around that level until such time as final disintegration takes place. But there is a fallacy in thus line of thought. (writes William 11. Pick, B.Sc., F.R.A.S., in the “(Newcastle •Weekly Chronicle”). True that the pressure does very greatly' increase, but the .consistency of density of the water does not To consider these two factors in more detail: 33 ft of salt water is roughly equal to 30in of mercury, that is to say, roughly to one atmosphere pressure or 151 bto the square inch. At 66ft down ,therefore, the pressure is 301 b to the square inch, excluding the pressure due to the atmosphere outside, and at 00ft., •loll) to the square inch, and so on, until at a depth of 4,000 fathoms (2-1,000 ft) the pressure would attain 7 : 20 atmospheres, or nearly five tons to the square inch. Compressibility is, however, marked bv far less striking increase. Water is compressible only by about one twentythousandth of its volume for one atmosphere of pressure, and at 4,000 fathoms, 10,500 cubic.feet of surface water would be compressed into the compass of 10,000 cubic feet. In other words, the density only increases a little. The idea, then’ that the depths of the ocean are littered with floating ships and debris is not justified—all such things ■

TREMENDOUS PRESSURE

arc probably resting quietly on the bottom. A ship sinking would go on sinking until its fall was arrested by the ocean bed. Changes l thc-re would be due to implosion, that is “explosion inwards.” For example, every hermetic-ally closed chamber would be so imploded because the ever-increasing pressure on the outside could not be counter-balanced on the inside, but that would be about all—and actual experiments done on bodies of animals by lowering them to great depths on the end of a line reveal that these bodies when pulled up are little altered in appearance. Strange effects are noticed, however, in the case of fish whose natural habitation is at profound -depths and whose bodies are, therefore, framed to withstand tremendous pressure and to function in tremendous pressure. If through any caprice of Mother Ocean, any untoward suboceanic upheaval, such a fish gets elevated from the level in which it normally has its being, the decrease of pressure experienced causes its swimming bladders to distend. This expan sion moans a reduction in its specific gravity, that is, of its weight per cubic volume, and it begins to float upward. Up to a certain limit it -can, by muscular reactions, counteract this upward movement. From that point the fish inevitably goes upward and upward, powerless to stop the rise, fumbling to the surface grotesquely. The pressure on it steadily gets less and less as it tumbles onward, and, in conse quenee, its organs become gradually more and more distended, until so much distension is obtained that death results, death due to under pressure and not to over. -