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INTRODUCTION 



Some four centuries before the birth of 

 Christ, Aristotle wrote of small "diving bells" 

 used by sponge divers who regularly worked 

 at depths of 75 to 100 feet. The bells were 

 inverted bowls weighted down by stones. The 

 divers would stick their heads in them to 

 replenish their air without surfacing. The air 

 in the bells, in turn, was resupplied by 

 weighted skins filled with air and lowered 

 from the surface. 



In 1620 A. D. a Dutchman, Cornelius van 

 Drebel, is said to have constructed a sub- 

 mersible under contract to King James I of 

 England. It was operated by 12 rowers, with 

 leather sleeves waterproofing the oar-ports. 

 Cans containing some "secret substance" 

 (soda lime?) were opened periodically to pu- 



rify the air. It is said that the craft navi- 

 gated the Thames River at depths of 12 to 15 

 feet for several hours. 



In 1707 Dr. Edmund Halley (of Halley's 

 Comet fame) built a diving bell with a limited 

 "lock-out" capability. It had glass ports 

 above to light the inside of the bell, provi- 

 sions for replenishing its air and crude, um- 

 bilically-supplied diving helmets which per- 

 mitted divers to walk around outside — so 

 long as they didn't lower their heads below 

 the water level in the bell! 



In the late 1770's Connecticut Yankee Dr. 

 David Bushnell built and operated a small 

 wooden submarine designed to attach mines 

 to and blow up British warships. After sev- 

 eral abortive attempts, TURTLE, as the ve- 



