RESPIRATION 



335 



In order to enable the diver to sink and stand firmly on the 

 bottom, the dress is weighted with 4O-pound leaden weights, 

 back and forward, as shown, with 16 pounds of lead on each 

 boot about 112 pounds of lead in all. Besides the air pipe, the 

 diver is connected with the surface by a so-called life line, which 

 usually contains a telephone wire. He goes down by a rope at- 



Figure 77. 

 Helmet and section of outlet valve. 



tached to a heavy weight which has been lowered to the bottom 

 previously, and on reaching the bottom he takes with him a line 

 attached to this weight, so that he can always find the rope again. 

 As a diver enters the water, the superfluous air in his dress is 

 driven out through the outlet valve by the pressure of the water 

 round his legs and body. The water seems to grip him all round. 

 If the valve is freely open he feels his breathing somewhat 



