48 



THE AUSTRALIAN MUSEUM MAGAZINE. 



The Depths of the Sea. 



By Charles Hedlev. 



To a man viewing the open ocean lor 

 the first time probably its most strik- 

 ing feature -would be the level of its 

 wide expanse. And wlien lie thougm 

 of the land that lies under that water 

 he might naturally imagine the l)ed of 

 the sea as expanding in a plain like 

 the surface. 



But this would be a wrong conjec- 

 ture, for, though there are jDlains at 

 the bottom of the sea, plains indeed 

 that are broader and more monotonous 

 than any plains of the land, there are 

 also valleys, uplands and volcanic 

 cones. If they had not been already 

 found and measured, their existence 

 would have been assumed by geograjili- 

 ers. For, as this globe aged, it grew 

 through stages of gas or molten rock 

 to coolness and solidity, and, after the 

 crust had cooled and set hard, the core 

 inside continued to cool and shrink. 

 As the outer shell collapsed to lit this 

 shrivelled core, wrinkles appeared on 

 the surface; such wrinkles, which are 

 valleys and mountain ranges, must oc- 

 cur indifferently on land or under the 

 sea all over the world. 



Under the sea the landscape is ex- 

 pressed in smoother lines than in ter- 

 restrial scenery. Here are no tower- 

 ing cliffs, ravines, or splintered crags, 

 no waterfalls, forests, or glaciers. The 

 features of alpine scenery have been 

 carved out by rain, frost, and wind, but 

 these agencies do not ()]>erate beneath 

 the sea. 



It happens that the highest height of 

 the land and the deepest depth of the 

 sea just balance one another. A de- 

 pression in the North Pacific Ocean 

 about a hundred miles south-east of the 

 island of Guam is the match t'(n- ^It. 

 Everest in the Himalaya. 



An explorer examines the islands, 

 mountains, or rivers, that he passes 

 witli compass and telescope; any peak 

 or Dosition that he can '^ee, however 

 distant or inaccessible, can be measured 

 and placed on the map. But the moun- 

 tains under the sea. that no human eye 

 ever has seen or will ever see, must be 

 studied in other ways. A blind man. 



who cannot see, must feel his way, so 

 navigators feel their way to the depths 

 of the sea with sounding line and ther- 

 mometer. 



Before the impulse of the trade 

 winds the surface ot the sea is pushed 

 away from the ecjuator and is driven on 

 to form great warm currents like the 

 Gulf Stream. After long wanderings 

 these rivers of the ocean sink out of 

 sight in the cold polar seas. Movement 

 in deeper water continues the circula- 

 tion until at last great volumes well up 

 to the surface to restore the level de- 

 pleted by the trade winds and thus 

 completes the cycle. So in deep water 

 there is a constant trickle of icy w^ater, 

 a few degrees above freezing point, 

 from polar to ecjuatorial seas. 



These cl^rrents maintain the life of 

 the sea by spreading food and oxygen; 

 they cool the torrid and they warm the 

 frigid zones. Where the circulation is 

 free, the temperature readings dimin- 

 ish gradually from the surface to the 

 floor, but where the walls of a submar- 

 ine basin obstruct the circulation, the 

 temperature falls onl}' to the level of 

 that basin rim. Beneath this horizon 

 the dead water maintains a uniform 

 temperature. 



These dejDths are not only cold but 

 dark. Water that seems transparent 

 for a few inches becomes opaque in a 

 few fathoms, and no light can struggle 

 down through miles of water. The 

 myriad organisms that float in the sea 

 would alone screen off the light. It has 

 been suggested that different elements 

 of the spectrum attain different depths; 

 that, descending, we should reach a 

 world of purple glow and pass a reg- 

 ion where all shone red as if the light 

 cam,e through stained glass windows. 

 But down lieyond all this, there lies an 

 abyss of blackest and eternal night, il- 

 lumined only by the sheen and glitter 

 of phosphorescence. As a consequence 

 of the absence of light, vegetation dis- 

 appears at about one hundred fathoms 

 from the surface. In the gloomy depths 

 beyond, all creatures are perforce car- 

 nivorous. Here many animals go 



