350 RESPIRATION 



danger. These figures show also in a clear way, the advantages oi 

 cutting down the duration of stay on the bottom. It appears from 

 Figure 90 that with the short stay on the bottom the more slowly 

 saturating parts of the body have not time to reach a dangerous 

 degree of saturation, though they might do so if similar dives 

 were repeated after short intervals on one day. 



With a long exposure to a high air pressure the time required 

 for safe decompression, even by the stage method, becomes much 

 too long for ordinary diving work. Figure 92 shows, for instance, 

 that it would take nearly five hours by the stage method, and ten 

 hours with uniform decompression, for completely safe decom- 

 pression after a stay of some hours under a pressure of 35^^ 

 fathoms of water, or an excess pressure of 6J4 atmospheres. 

 In the ordinary diving table, therefore, the stay on the bottom is 

 so limited that the diver can be decompressed safely in half an 

 hour. Nevertheless, it may happen that it is justifiable to stay 

 longer, or that a diver's air pipe is fouled by something on a wreck 

 and even that he cannot be liberated till the tide slackens or turns. 

 To meet such cases a supplementary table was drawn up. These 

 two tables are reproduced below. 



Since the introduction iijto the British Navy twelve years ago 

 of the method of decompression embodied in the tables, with the 

 corresponding regulations as to air supply and testing of the 

 pumps, deep diving has been conducted with comfort and safety 

 to the divers, so that compressed-air illness has now practically 

 disappeared except in isolated cases where from one cause or 

 another the regulations have not been carried out. When a medi- 

 cal compressed-air chamber is available, it is justifiable to cut 

 down the time for the last wearisome stages of the decompression, 

 and so extend the time on the bottom. This has been cautiously 

 tried under Commander Damant's supervision, but the result was 

 that the divers began to suffer from *'bends." These could easily 

 be relieved in the chamber, but much loss of time and incon- 

 venience resulted, and the "bends" were apt to recur. It seemed 

 better to keep the chamber as a precaution against emergencies or 

 unforeseen accidents. I calculated the tables with great care on 

 the theoretical lines borne out by the experiments and in the 

 light of all the available evidence from human experience ; and it 

 appears that the times cannot be cut down without risk of trouble, 

 unless the divers are placed in the chamber as a matter of routin 

 after each dive. 



If a diver develops serious symptoms of compressed-air illness, 



