Note on Maps xix 



ern Asia, Europe, North America, and the Antarctic. We should 

 thus get three triangular continents depending south — and we have 

 these in Asia plus Australia, Europe plus Africa, and the Americas — 

 and three triangular oceans running up between them, which we 

 also have in the Indian, Atlantic, and Pacific complexes. This would 

 leave a flat triangular area at the top which should be filled with 

 an ocean — the Arctic Ocean. We have just such a roughly triangu- 

 lar area of water there, but we still need to know at least one more 

 over-all fact. 



The true oceans are great areas of apparently permanent depres- 

 sion that have never been dry land. Their rocky bottoms are said 

 to be covered with the second layer of the earth's surface, known 

 as the sima (silicon-magnesium predominating), as opposed to the 

 continents which are bits of the outermost layer, known as the sial 

 (silicon-aluminum predominating). The continents of sial are said 

 to float on the sima. The continental rafts are at present partially 

 flooded or sunken so that a shelf extends seaward from all of them 

 to a varying degree in all directions towards the oceans. They are 

 notably wide off the southeastern coast of South America and to the 

 east of Australia. These shelves are comparatively shallow, that is 

 to say vis-a-vis the true oceans, but they are also clearly defined. 

 Upon them, and upon them alone, are to be found what are called 

 terrigenous deposits, namely, sediments derived from land surfaces 

 and washed into the sea. Beneath the true oceans are only five kinds 

 of silts, formed from meteoric material that descends from the 

 sky, or muds derived from the coverings of tiny single-celled animals 

 that die in the water above or from those of little free-swimming 

 shellfish. The division between terrigenous deposits and these others 

 marks the boundaries of the true oceans. All the rest of the water 

 constitutes seas^ which are something quite different. 



The distribution and boundaries of the true oceans are of the 

 utmost importance to a proper understanding of the natural history 

 of whales and the history of their pursuit. Whales are not, as is 

 often supposed even scientifically, cosmopolitan. Almost all of them 

 are strictly confined to either oceans or seas — and very often to 

 specific oceans or seas — while there are others that do not even enter 

 the seas but are limited to the diadem of inlets, bays, estuaries, and 

 other shallows that encircle them, just as the latter do the oceans. A 



