696 



DEPTHS OF THE OCEAN 



The viscosity exhibits, as shown in Fig. 506, a similar course. 

 We find a much greater viscosity in the waters of the Norwegian 

 Sea than in those of the Atlantic. The conditions of viscosity at 

 a depth of 50 metres in the Norwegian Sea correspond to the 

 conditions at about 800 metres in the Atlantic, where at the 

 surface we meet water-layers of small viscosity : " thin water." 



If now we compare the distribution of animal life, as 



46 



Fig. 506. — Distribution of Viscosity (see text) from the Sargasso Sea (Station 63) 



TO Lofoten (Norwegian Sea). 



100 = the viscosity of distilled water at 0° C. 



described in Chapter IX., with these facts, we may clearly 

 understand many of the peculiarities of distribution. 

 Warm-water From the distribution of specific gravity and viscosity it 

 oceanic life. fQ^Q^g l-j^g^j- jj^ light, thin, and warm oceanic waters only those 

 animals are found which have lowered their specific gravity by 

 the aid of light substances (fats, water), or have increased their 

 surface resistance by reducing their size or by developing 

 special organs for floating. To the first type belong the 

 Siphonophores [Pkysalia, PJiysophoi'a, Agahnopsis, and many 

 others), besides Medusae, Salpse, Doliolum, Pyrosoma, and 



