Subsurface observations have been made by submersibles and by 

 divers operating either fronn the surface or from underwater laboratories. 



Cromie, William J. 



Exploring the Secrets of the Sea, Prentice-Hall, 1962. 

 Yasso, Warren E. 



Oceanography, A Study of Inner Space, Holt, Rinehart and 



Winston, 1965. 



76 



