ILLUMINATING THE OCEANS 



ments can be met by free-flooded lamps, in which the 

 hydrostatic pressure is resisted by the glass envelope. 



Operating in direct contact with the water, their 

 success depends on what is called the implosion resistance 

 of that envelope — implosion being the bursting of a vessel 

 inwards under pressure. Success has been attained with 

 this new lamp after numerous experiments. The proto- 

 types showed that the outer surfaces of the bulbs used 

 were cooled effectively by immersion in the sea, but the 

 inner surfaces were heated by radiation and conduction 

 from the filaments, operating through the gas fillings. 

 Bulb failures were soon found to be due to the severe 

 thermal stresses set up within them, rather than the 

 pressure of water from without. Using a wall thickness 

 of about a millimetre in conjunction with a specially 

 shaped bulb, the present lamp came into existence ; one 

 which can withstand a pressure of 650 lb. a square inch 

 — equivalent to a depth of 1,300 feet. 



As the new lamp is operated only when fully sub- 

 merged, it has been possible to reduce the size of the bulb 

 and improve its resistance to implosion; for full advan- 

 tage is now taken of the cooling effect of the sea water. 

 The connections to the lamp are protected by a sealing 

 "muff" of moulded rubber, which helps to provide a 

 complete lighting unit for underwater use, in conjunction 

 with the light-weight fitting originally designed. The 

 units first used, of which the new lamp is the latest 

 development, were first operated in the search for the 

 Comet aircraft which crashed in 1954. During recent 

 trials by the diving ship H.M.S. Reclaim there were no 

 failures : the exhaustive tests showing that one diver can 

 handle four of these lamps during underwater inspection 

 work, while directing salvage operations. The lamp can 

 also be used for underwater television. 



The lighting device just described is but one of 

 numerous inventions perfected in recent years for deep- 

 sea exploration, and may serve to indicate the enormous 



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