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BUMPER SUB INSPECTION - Bruce C. Heezen, right, of Columbia University's Lamont-Doherty Geological Observatory, and Ian D. MacGregor, center, of the University of California at Davis, Cruise Co-Chief Scientists on Leg 20 of the Deep Sea Drilling Project, discuss with Cruise Operations Manager Lamar P. Hayes the function of a bumper sub aboard D/V Glomar Challenger. Normally, three bumper subs each with a five-foot stroke - are used on a drilling string which permits the bottom hole assembly and drill bit to remain at the bottom of the bore-hole by compensating for the heave of the vessel while in the process of drilling and recovering sedientary core material. 1971

BUMPER SUB INSPECTION - Bruce C. Heezen, right, of Columbia University's Lamont-Doherty Geological Observatory, and Ian D....