INHABITED REGIONS OF THE OCEAN. 



121 



dangerous their neighbourhooil is to the sailor >\ ho 

 is compelled to wiuter in these inhospitable regions. 



Thus, heat on tlie one hand, an 1 cold on the other, 

 arrest the extension of life beneath the ocean. 



It is not necessary to descend far below the sur- 



K^. Hie Hippocampus, 



face of the sea to find the limits of tliat vital zone 

 which seems to ns at first so immensely extended. 

 At slight depths every undulation of the surface 

 acts as a disturbing cause, and obscures vision by 

 rapid alternations of light and shade. Soo:i the 



