Fig. 20. The Evolution of Human Diving. The left column shows the 

 various attempts at drawing air down from above to the diver, from the ele- 

 phant's trunk to the modern helmet and hose. The right column illustrates the 

 gradual attainment of success in actually conveying a supply of air beneath the 

 surface. The water beetle does this, and points the way, from the inverted vase 

 of Aristode to the self-contained bathysphere. 



