The Geographical Journal (Volume 3)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: colour, and the more delicate tow-nets were at such times so filled with these animals, that they occasionally burst on being hauled on board ship. These small crustaceans are in turn the chief food of the fishes, penguins, seals, and whales, which abound in the waters of the Great Southern Ocean. Organisms such as the Diatoms and Radiolaria, which secrete silica, and the Foraminifera and Pteropods, which secrete carbonate of lime, are, on account of their distribution, the most interesting of all the pelagic creatures captured in the surface and sub-surface waters of the ocean. Near Antarctic land the deposits at the bottom of the sea are, as already stated, mostly made up of rock-fragments and detritus from the snow-clad Antarctic continent. A little to the north the number of these particles decreases, and they are largely replaced by the dead GLOBIGERINA OOZE FBOM 1900 FATHOMS IN THE ATLANTIC. MAGNIFIED 25 DIAMETERS. frustules of Diatoms and Radiolaria, and then we find a pure white siliceous deposit at the bottom, which is called a Diatom Ooze. Still further to the north, when the influence of the warm northern currents commences to be felt, the Diatoms are largely replaced on the surface by the calcareous shells of Foraminifera and Pteropods, and at the bottom of the sea in these latitudes the Diatom Ooze gives place to a pinkish-white Globigerina Ooze, composed chiefly of carbonate of lime. Still further to the north, about the latitude of 40 S., the sea is often about 3 miles in depth, and in such depths where far removed from continental land, the calcareous shells are for the most part dissolved, and there is a very remarkable deposit at the bottom, composed of a fine Red Clay, manganese nodules, zeolitic crystals, magnetic and metallic spherules of extra-terre...