Leeboard. When sailing into the wind, a tacking ship may experience a lot of leeward drift, which forces the ship to go sideways with little progress forward. To correct this problem the Chinese invented the leeboard in the eighth century. This device was first mentioned in Li Chuan’s Instruction Manual of the White and Dark Planet (759). The leeboard was a board lowered into the water on the lee side of the ship to apply pressure on the water, stopping drift in that direction and holding the ship erect. Some leeboards would be lowered from a slot in the center of the ship and were therefore called centerboards. The Dutch and Portuguese learned of the leeboard while trading in China, but they did not adopt it until the sixteenth century.
Paddle-Wheel Warship. The paddle-wheel warship arose in the Song age (960-1279). Without rudders, it was propelled by a complicated system of paddle wheels on both sides and the stern. Also called the “wheel ship,” the paddle wheeler had an average length of three hundred feet and a complement of eight hundred sailors and marines. Such a vessel generated 50 horsepower with an average speed of 3.5 to 4 knots. A fast vessel, it could dart in and out of enemy formations and inflict great damage. However, it was not suited for oceanic voyages because of the strong currents and rough waves. Some paddle-wheel war-ships even had rammers fitted to their prows. In 1168 Admiral Shi Zhengzhi built a 100-ton warship propelled by a single twelve-bladed wheel. During the Yuan dynasty (1279-1368), however, the use of paddle wheelers declined rapidly as a result of most naval operations occurring on the sea instead of inland waterways.
Spillway. Before 984, Chinese boats, which did not have any keels and were almost flat-bottomed, could only move between lower and higher water levels in canals over double slipways. Consequently, a spillway was used to regulate water flow. It extended ramps into the water, and a ship would approach and be fastened to ropes turned by ox-powered capstans. Within two or three minutes the ship would be hauled up the ramp to the higher level and for a moment would balance insecurely in the air. Then it would shoot forward, scudding down the canal at a level several feet higher than it had started. Travelers and sailors had to tie themselves firmly to the boat so as to prevent being thrown about and wounded. The disadvantage of this technique was that boats and their cargoes often sustained severe damage. Many times bandits and corrupt officials would wait for just such moments to loot the vessels and their contents. There is also historical evidence that suggests occasionally boats were brutally handled on purpose or were artificially weakened in order to create “accidents.”
Canal Pound-Lock. Since grain was the ordinary tax payment throughout imperial China (617-1644), and transportation of it to central repositories and warehouses was the lifeblood of the dynasties, any considerable interruption of this shipping would generate an extremely grave social and political crisis. To eliminate the stealing of grain
during canal transport, Qiao Weiyo, assistant commissioner of transport for Huainan, invented in 984 the canal pound-lock. He built two large “hanging gates” at the third dam along the West River near Huaiyin. The 250 feet between the two gates was then covered with a great roof like a hut. After a boat passed the first gate, it closed behind the vessel. The water level in the lock then either rose or fell to match the level of the water toward which the boat was sailing. The other gate then opened and let the boat go through.
Advantages. Water levels in an average canal differed by 4 or 5 feet at each lock, and over its entire length a canal could rise more than 100 feet above sea level. (The Grand Canal rose 138 feet above sea level.) However, many canals in China became dry in the summer, and several weeks would have to pass before enough water had been accumulated for flash-gates to be opened in order to let boats enter. The introduction of pound-locks helped to save valuable water resources. Only one lock was used each time, so that the canals, by saving water, could extend the time of their usefulness. More importantly, the previous corrupt practices became limited, and the passage of the ships went on without any obstructions.
Decline. The use of pound-lock gates declined because of social changes. After the Mongols moved the capital to Beijing, it was not feasible to transport the whole imperial grain tribute to the city by canal. As a result they shipped about one-half of the entire annual supplies by sea. As time went on, the need for large boats on the canals was reduced, many smaller vessels came into use, and the pound locks fell into disrepair. While this device became less useful in China, Europeans began to adopt it in 1373.
Post Stations. The Tang dynasty (618-907) provided the greatest expansion of waterways, connecting the Yellow River with the Yangzi (Yangtze) and Hangzhou rivers through the Grand Canal. The Tang court also constructed roads along both banks of the canal. These roads and an accompanying network of post stations allowed the government to receive news and send out orders all over the empire rapidly. Elms and willows planted along the sides of the road provided travelers with shade. The post stations, 25 to 30 miles apart, each had 200 horses. The hostelries at the stations had beds with silk coverlets for high-ranking emissaries. On the same roads, there was usually a runner service with stations every three miles. On average, a mes-sage could travel up to 300 miles in one day (longer if emergency circumstances warranted night riding and night running).
Derk Bodde, Chinese Thought, Society, and Science: The Intellectual and Social Background of Science and Technology in Pre-Modern China (Honolulu: University of Hawaii Press, 1991).
E-tun Sun and Shiou-chuan Sun, trans., T’ien-kung k’ai-wu: Chinese Technology in the Seventeenth Century (University Park: Pennsylvania State University Press, 1966).