Because of the Dujiangyan dam system, the plains of eastern Sichuan became an affluent agricultural center of China. Ancient records called the area "Land of Abundance." With the dam still operating, the Sichuan plains remain an agricultural center today. In 1974, two water gauges, carved in a.d. 168, were found in the riverbed by the site of Li Bings dam. They seem to have been replacements for the original water gauge statues. One of them is the oldest Chinese stone figure ever found of an identifiable individual. It is a statue of Li Bing. The original gauges he had used depicted gods of flood control. Four centuries after his death, he was considered to be one of these gods.
Li Bing made a very simple but pivotal discovery. By his time, Sichuan had long been a salt-producing area. Salt is known to have been made in Sichuan as early as 3000 b.c. But it was Li Bing who found that the natural brine, from which the salt was made, did not originate in the pools where it was found but seeped up from underground. In 252 b.c., he ordered the drilling of the worlds first brine wells.
These first wells had wide mouths, more like an open pit, though some went deeper than 300 feet. As the Chinese learned how to drill, the shafts got narrower and the wells deeper. But sometimes the people who dug the wells would inexplicably become weak, get sick, lie down, and die. Occasionally, a tremendous explosion would kill an entire crew or flames spit out from the bore holes. Gradually, the salt workers and their communities realized that an evil spirit from some underworld was rising up through the holes they were digging. By 68 b.c., two wells, one in Sichuan and one in neighboring Shaanxi, became infamous as sites where the evil spirit emerged. Once a year the governors of the respective provinces would visit these wells and make offerings.
By a.d. 100, the well workers, understanding that the disturbances were caused by an invisible substance, found the holes where it came out of the ground, lit them, and started placing pots close by. They could cook with it. Soon they learned to insulate bamboo tubes with mud and brine and pipe the invisible force to boiling houses. These boiling houses were open sheds where pots of brine cooked until the water evaporated and left salt crystals. By a.d. 200, the boiling houses had iron pots heated by gas flames. This is the first known use of natural gas in the world.
Salt makers learned to drill and shore up a narrow shaft, which allowed them to go deeper. They extracted the brine by means of a long bamboo tube which fit down the shaft. At the bottom of the tube was a leather valve. The weight of the water would force the valve shut while the long tube was hauled out. Then the tube was suspended over a tank, where a poke from a stick would open the valve and release the brine into the tank. The tank was connected to bamboo piping that led to the boiling house. Other bamboo pipes, planted just below the wellhead to capture escaping gas, also went to the boiling house.
Bamboo piping, which was probably first made in Sichuan, is salt resistant, and the salt kills algae and microbes that would cause rot. The joints were sealed either with mud or with a mixture of tung oil and lime. From the piping at Sichuan brine works, Chinese throughout the country learned to build irrigation and plumbing systems. Farms, villages, and even houses were built with bamboo plumbing. By the Middle Ages, the time of the Norman conquest of England, Su Dongpo, a bureaucrat born in Sichuan, was building sophisticated bamboo urban plumbing. Large bamboo water mains were installed in Hangzhou in 1089 and in Canton in 1096. Holes and ventilators were installed for dealing with both blockage and air pockets.
Salt producers spread out bamboo piping over the countryside with seeming chaos like the web of a monster spider. The pipes were laid over the landscape to use gravity wherever possible, rising and falling like a roller coaster, with loops to create long downhill runs.
Salt by Mark Kurlansky. Copyright Mark Kurlansky 2001. Reproduced by permission of the publisher, Walker Books. All rights reserved. No part of this book may be reproduced without written permission from the publisher.
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