Many attempts have been made in the past to dampen 

 such ship motion for purposes of personal comfort, military 

 operations, and scientific research. Bilge keels, gyro 

 stabilizers, hydraulic systems, flow tanks, and mechanical 

 devices have been used to lessen the effects of roll and 

 pitch. But heave of the vessel itself, caused by the periodic 

 passing of wave troughs and crests, has never been appre- 

 ciably reduced. 



In a different approach, efforts have been made, and 

 some with moderate success, to remove or reduce exces- 

 sive pull or tension changes in wire lowering rope. Spring 

 accumulators and hydraulic pistons mounted on fair leads 

 and head sheaves, air systems, and accelerometers have 

 been employed by oceanographers and engineers to provide 

 constant wire tension in many marine operations. None of 

 these attempts has been 100 per cent successful. Accumu- 

 lators and hydraulic pistons have only dampened the re- 

 sultant overload strains and movements to some degree. 

 Differential systems employing compressed air springs and 

 sheaves have been defeated by friction, phasing, and timing, 

 and other systems by cost, weight, and size. 



A particularly urgent need exists for a simple, ef- 

 fective, and almost frictionless device to provide depth 

 control of deep-sea cameras. These cameras are self- 

 contained units that are lowered to specific distances above 

 the sea floor which they photograph at preset time intervals 

 while being towed by drifting platforms (vessels). Camera 

 lenses and electronic light sources are limited to short 

 distances when used underwater because of the strong ab- 

 sorption and scattering of light by water and suspended 

 particles. 2 To obtain good color rendition and sharp focus, 

 it is necessary to shoot close-ups at carefully controlled 



2. Schenck, H. , Jr. and Kendall, H. , Underwater Photog - 

 raphy, Cornell Maritime Press, 1954 



