348 



RESPIRATION 



rate was calculated in stages, each of which represents a reduc- 

 tion in depth of lo feet, so that a diver is stopped by signal at every 

 ten feet of ascent. 



Figure 90 represents what is happening during a dive to 28 

 fathoms, with the stay on the bottom limited to 14 minutes, and 



75 



^60 



^ 

 ^ 



45 



30 



15 





/o 



15 



50 35 40 45 



20 25 



Figure 90. 

 Diving to 168 feet by new method: Diver 14 minutes on the bottom and 46 

 minutes under water. The curves from above downward represent, respectively, 

 the variations in saturation of parts of the body which half saturate in 5, 10, 20, 

 40, and 75 minutes; the thick line representing the air pressure. 



the new method carried out of rapid descent and ascent by stages. 

 It will be seen that when the diver reaches surface, the maximum 

 condition of supersaturation with nitrogen in any part of the body 

 corresponds to only 17J/2 pounds per .square inch (or 1.17 atmos- 

 pheres) of air pressure. This leaves a margin of safety. Figure 91 

 shows what happened by the old method, with the same time on 



