OXYGEN GAS FOR ATHLETES 265 



of the lungs in expiration. With such an apparatus a 

 diver can safely remain under water at a depth of 60 ft, 

 and walk about and explore for as long as two hours. A 

 most important application of this self-contained diving 

 apparatus is found in its use in the exploration of mines, 

 where smoke or gaseous products resulting from an 

 explosion render it impossible for rescue parties to pene- 

 trate without its use. It has been the means of saving 

 many lives in such circumstances. A form of this 

 apparatus is made in which the oxygen is supplied, not 

 by a cylinder of compressed gas, but by granules of a 

 chemical compound called pneumatogen, a peroxide of 

 sodium and potassium, which when breathed into absorbs 

 carbonic acid from the air expired by the lungs, and gives 

 off pure oxygen. Submarine ships are now being provided 

 with a dress or outfit of this description for each member 

 of the crew, so that in the case of the entrance of water 

 into the submarine, every man can put on his "oxygen 

 helmet," and one by one, when the ship is full of water, 

 they can pass out by the conning tower and float to the 

 surface. The perfected diving dress, with self-contained 

 diluted oxygen supply and other improvements, has been 

 constructed by Siebe, Gorman, and Co., and was 

 exhibited by Dr. Leonard Hill at a soiree of the Royal 

 Society. 



