Floating of a dock based on Archimedes Principle of Buoyancy technique of construction created dynamism on water-body. The mechanism of crane is found to be an extremely important for the maritime industry to salvage grounded ships. The earliest known description of a floating dock found in 1560. An old woodcut print shows a ship flanked by two large floating supporting towers, forming a roof above the vessel (plate 3A). The ship is pulled in an upright position by a number of ropes attached to the superstructure. Usage of crane is found from ancient period. However, a surviving 1413 built crane (plate 3B) in Germany displays unique feature of crane mechanism. The application of lever is greatly used for building construction purposes (plate 3C). Stacking up structural elements from ground to the upper levels depends on such crane mechanism.
