To meet the practical needs , the ancient Chinese displayed a high intelligence in conscientious observation and scientific abstraction . First , they invented the weighing apparatuses .
The earliest Chinese weighing apparatus consisted of a stick , hanging an object to be weighed at one end and stones at the other end . They found out the middle point of the stick by measuring with the hand , and tied a knot at the middle point for lifting up the stick . They adjusted the various sizes of stones to make the stick horizontal . The stones were weighed to determine the weight of the object weighed .
In the book “Records of Master Mo” written in the fourth century B.C. a proposition was put forward , which displayed a deep understanding of the ancient Chinese of the lever principle . The proposition asserted , “weighing must be balanced.” It called the sliding weights of a steelyard the “quan” and the object weighed the “zhong” . It called the side from the fulcrum to the objects weighed the “ben” , and the side from the fulcrum to the sliding weights the “biao” . Master Mo and his disciples pointed out : “When one side is heavier , this side will decline , … the longer side or the heavier weight will decline ; the shorter side or the lighter weight will tilt upward .” This proposition involves the principle that balance not only depends on the force or weight but also depends on the lengths on either side of the fulcrum . The rudimentary principle of balance embodied in the ancient weighing apparatus was in general conformity with the lever principle discovered by Archimedes . Actually the ancient Chinese had invented the balance and the lever much earlier and utilized them in a more advanced manner than what was recorded in the “Records of Master Mo” .
A ceramic model ship in the Eastern Han Dynasty was unearthed in ceramic modern ship in the Eastern Han Dynasty was unearthed in Guangzhou . An axial rudder was found at its stern . It was transitional from the long oar rudder to the axial turning rudder . Between the second and fourth centuries A.D. , the true axial turning rudder was used already in China , which was important for raising ship-operating efficiency . In about the twelfth century A.D. both the water-tight compartments and the axial turning rudder spread westward to the Mediterranean via the Indian Ocean . In the eleventh century A. D. the Chinese already invented the balance rudder and the holed rudder , both of which were only found in Europe at the eighteenth century A.D.
The ancient Chinese balance consisted of a bamboo beam , a silk thread knot as the holding knob and two copper 
pans hung at the two ends of the beam . When weighing an object , gold ornamental ring weights (called right “quan”) , carved with weight graduations were used . This small balance can weigh an object at precision of six ten-thousandth of a jin (1 jin = 1/2 kg .) . The weight of ring quans increased multiply , from one “zhu” (0.6 gram) , two “zhu” , three “zhu” , six “zhu” , twelve “zhu” , one “liang” (twenty four “zhu”) , two “liang” , four “liang” , half “jin” (eight “liang”) ,to one “jin” (sixteen “liang” , or 500 grams) . The high precision was a wonder .
