THE LOST RECOVERED.

Manawatu Herald, Volume XXXVIII, Issue 1619, 3 October 1916, Page 4

THE LOST RECOVERED.

MODERN DIVERS AND THEIR

, POWERS

, The matter of recovering some of the many ships which have been sunk , during the war or have been sunk through accident, is the subject of a recent article by an American writer, who states that the prospect of recovering sunken ships or the most valuable of the treasures that have gone down with them is far brighter now than it was four or live years ago. So great have been recent improvements in diving apparatus that a diver can now operate for limited periods even at the great depth of 300 feet. These improvements are largely due to deepsea diving experiments, conducted under the auspices of the Bureau of Construction of Repair of the Navy Department of the United States in 1914. Prior to that time the greatest depth reached by divers was 210 feet, this having been accomplished by two English officers during tests ca'rried out-by the British Admiralty in 1907.

At a depth of 300 feet the water pressure is 129.91 b., but notwithstanding this,' United Elates Navy expert divers have succeeded in remaining at a depth of from 300 ft. for from live to twenty minutes at a time, making examinations and observations in regal'd to a sunken •vessel (hat made its subsequent salvage possible;. This was in connection with the raising ot the submarine F 4, which sank near Honolulu on 25th March, 1915. This is the only instance in history that a sunken vessel has been recovered jrom a depth of 300 ft. The article', after giving a sketch of the history of diving, states that the necessity of having the air pressure within the diving dress compensate the external water pressure, thus .subjecting the diver to pressure directly proportionate to the depth to which he descends, is the dangerous element in dee]) sea diving. Exposure to the great pressures of the ocean is apt to be followed by what is known as “caison disease,” the symptoms including pains in the joints and muscles, deafness, embarrassed breathing, fainting, etc., sometimes resultingin death. These only appear after the pressure has been removed. Experiments show that when the pressure is suddenly relieved the gas is liberated in bubbles within the body, and these bubbles are the cause of the trouble. It has been found, however, that it the pressure is relieved gradually the bubbles are not formed, because the gas comes out in solution slowly, and is got rid of by the heart and lungs.

“To prevent these effects the withdrawal of the air pressure. —in in other words, the decompression — should be slow,”"concludes the article. “Hence, the divers’ ascent must be regulated accordingly, and the deeper he has been the slower and longer must be the periods for decompression. It was particularly in regard to this matter of decompression that the experiments of the United States Navy Department in 1914 led to improved methods, enabling the divers to descend to 300 ft. below the surface.

“Being able to safely observe and direct the work of rescue at such a depth, and with modern lifting apparatus, who can say that the recovery of ancient treasures, of sunken Spanish galleons, of hundreds of more recent wrecks of merchant vessels, and finally of many of the magnificent war vessels that have been sent to the bottom during (he present war is an idle dream?”