<P> The most important nautical innovation of the Song period seems to have been the introduction of the magnetic mariner's compass, which permitted accurate navigation on the open sea regardless of the weather . The magnetized compass needle--known in Chinese as the "south - pointing needle"--was first described by Shen Kuo in his 1088 Dream Pool Essays and first mentioned in active use by sailors in Zhu Yu's 1119 Pingzhou Table Talks . </P> <P> There were other considerable advancements in hydraulic engineering and nautical technology during the Song dynasty . The 10th - century invention of the pound lock for canal systems allowed different water levels to be raised and lowered for separated segments of a canal, which significantly aided the safety of canal traffic and allowed for larger barges . There was the Song - era innovation of watertight bulkhead compartments that allowed damage to hulls without sinking the ships . If ships were damaged, the Chinese of the 11th century employed drydocks to repair them while suspended out of the water . The Song used crossbeams to brace the ribs of ships in order to strengthen them in a skeletal - like structure . Stern - mounted rudders had been mounted on Chinese ships since the 1st century, as evidenced with a preserved Han tomb model of a ship . In the Song period, the Chinese devised a way to mechanically raise and lower rudders in order for ships to travel in a wider range of water depths . The Song arranged the protruding teeth of anchors in a circular pattern instead of in one direction . David Graff and Robin Higham state that this arrangement "(made) them more reliable" for anchoring ships . </P> <P> Architecture during the Song period reached new heights of sophistication . Authors such as Yu Hao and Shen Kuo wrote books outlining the field of architectural layouts, craftsmanship, and structural engineering in the 10th and 11th centuries, respectively . Shen Kuo preserved the written dialogues of Yu Hao when describing technical issues such as slanting struts built into pagoda towers for diagonal wind bracing . Shen Kuo also preserved Yu's specified dimensions and units of measurement for various building types . The architect Li Jie (1065--1110), who published the Yingzao Fashi (' Treatise on Architectural Methods') in 1103, greatly expanded upon the works of Yu Hao and compiled the standard building codes used by the central government agencies and by craftsmen throughout the empire . He addressed the standard methods of construction, design, and applications of moats and fortifications, stonework, greater woodwork, lesser woodwork, wood - carving, turning and drilling, sawing, bamboo work, tiling, wall building, painting and decoration, brickwork, glazed tile making, and provided proportions for mortar formulas in masonry . In his book, Li provided detailed and vivid illustrations of architectural components and cross-sections of buildings . These illustrations displayed various applications of corbel brackets, cantilever arms, mortise and tenon work of tie beams and cross beams, and diagrams showing the various building types of halls in graded sizes . He also outlined the standard units of measurement and standard dimensional measurements of all building components described and illustrated in his book . </P> <P> Grandiose building projects were supported by the government, including the erection of towering Buddhist Chinese pagodas and the construction of enormous bridges (wood or stone, trestle or segmental arch bridge). Many of the pagoda towers built during the Song period were erected at heights that exceeded ten stories . Some of the most famous are the Iron Pagoda built in 1049 during the Northern Song and the Liuhe Pagoda built in 1165 during the Southern Song, although there were many others . The tallest is the Liaodi Pagoda of Hebei built in 1055, towering 84 m (276 ft) in total height . Some of the bridges reached lengths of 1,220 m (4,000 ft), with many being wide enough to allow two lanes of cart traffic simultaneously over a waterway or ravine . The government also oversaw construction of their own administrative offices, palace apartments, city fortifications, ancestral temples, and Buddhist temples . </P>

China reached its largest geographic size during which dynasty