Compressed Air Work And Diving 1909

36 COMPR ESSER) AIR WORK. powers of a man, which are generally consiclerecl to be about 3,000 ft.-Ibs. per minute. It would probably be better for very cleep dives to use a larger number of pumps with smaller capacity and also with a rather longer stroke than is customary. The increase in length of stroke would lessen the percentage loss due to cushion- ing. Another way to get over the difficulty is to fasten a rope in the middle of its length to both handles at the ends nearest the pump. As many men as necessary can then get hold of the four ends and help those who have hold of the handles. The work of the latter will then be reduced by about one-half, and they will also have to clo most work when the pump handles are in the most favourable position for force to be exerted by them. When three pumps are usecl they should be connected to a four-way junction piece with valves so that any one pump can be shut off or cletachecl if necessary. When the diver reaches the first stopping place one pump will be sufficient, as a little excess of CO2 will be an aclvantage rather than otherwise as it will tenel to stimulate the cliver’s circulation, and thus help him to get rid of his surplus nitrogen.* When the diver has nearly reachecl his first stopping place the pumps should be stoppeel for a moment, and the gauge tappeel in order to accurately find his position, and to stop him by signal at exaetly the right place. Pumps usecl for deep diving should be frequently tested for leakage and other losses. The methoel adopted by the Admiralty Committee was to connect up to a clry gas meter, and then by compressing the outsicle of the pipe any pressure re- quired could be obtained. It then only remained to * “ Diving Report,” p. 45,