National Geographic : 1947 Mar
Miracle Men of the Telephone 299 Dr. Bell Devised a Concrete' "Mulberry" Like Those Used in the Normandy Invasion He and F. W. Baldwin (left) designed it in 1916 to use as a dock on steeply sloping rocky bottom where piles could not be driven. After being launched like a ship, the concrete caisson was towed into position and sunk, as were the larger "Mulberrys" that formed artificial harbors for the Allied landings of 1944. Gilbert Grosvenor In Position, the Caisson Is Sunk by Pulling a Plug in Its Wooden Bottom Its underside was shaped to fit the contours of the lake floor as determined by soundings. Filled with rocks and topped with concrete, the dock served for many years at the inventor's summer home.