This 1952 cover depicts two enormous concrete caissons sitting in a natural drydock in Stony Point, N.Y. Each caisson is 360 x 82 x 32.5 ft. and weighs 27,000 tons. Along with a third caisson that is 367 x 87 x 28 ft and 19,000 tons (not pictured) they were cast in the dry in an abandoned clay pit off the west bank of the Hudson River, where seepage of water had formed a 2,100-ft-long, 650-ft-wide pond parallel to the river. After pumping the pond dry, shovels and draglines were used to remove 150,000 cu yd of mud, clay and silt. 5,300 tons of reinforcing steel was welded into assemblies, which gantry cranes placed ahead of wood forms, followed by a series of 36 pours. The completed watertight caissons were then towed 38 miles downriver and set atop pilings from the previous pier (destroyed in a fire in 1947) while their buoyancy supported 90% of the total load.…