Authors: Gavin Menzies
1434 (23 page)
Di Giorgio's piston pump is shown in the copy of his
Trattato di architettura
owned by Leonardo da Vinci, which is now in the Laurenzian Library in Florence. Leonardo improved upon di Giorgio's drawings.
In many ways, the Po resembles a smaller version of the Yangtze. Both rivers carry melting snows from the mountains eastward to the sea. Both suffer from flash floods and are controlled by a network of canals, locks, sluices, and dams. The waters of both are used to form extensive rice fields. The exact date when the Po was first utilized for rice is not known. Clearly it predated the 1475 letter, but by how much? I suggest it was after 1435, when Taccola's first drawings of pumps appear, and probably after 1438, when his drawings of lock and sluice gates first appear.
The combination of booming silk production in Florence and Venice and adequate food for the silk workers enabled “an extraordinary increase in silk production” between 1441 and 1461.
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By the 1480s silk had become “the main source of employment” for Florentine workers. The rise in silk production was mirrored by the rise in the Medici family's wealth, which was largely a product of financing the export of fine silk cloth. Florence had acquired the port of Pisa in 1405 and Leghorn in 1421 and could thereafter export her cloths to northern Europe.
The Florentine Renaissance was fueled by wealth, especially that of
the Medicis. The family was in exile when Pope Eugenius IV moved the pontificate from Rome to Florence in 1434, interceded with the opponents of the Medicis, and enabled the family to return to Florence. The Medicis once again became papal bankers and soon controlled Florence. As the future Pope Pius II said, “Political questions are settled at his [Cosimo's] house. The man he chooses holds officeâ¦. He it is who decides peace and war and controls the lawsâ¦. he is king in everything but name.”
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Christopher Hibbert, in
The House of Medici; Its Rise and Fall,
writes of Cosimo de' Medici: “Foreign rulers were advised to communicate with him personally and not to waste their time by approaching anyone else in Florence when any important decision was required. As the Florentine historian, Francesco Guicciardini, observed, âHe had a reputation such as probably no private citizen has ever enjoyed from the fall of Rome to our own day.'”
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Cosimo was at the heart of western Christendom. When popes visited Florence, they stayed in Medici palaces, enjoyed Medici hospitality, accepted Medici loans, and, in return, granted highly valuable concessions. For example, in 1460 huge deposits of alum, an essential ingredient in fulling cloth, were found near Civitavecchia in the Papal States. In 1466 the Medicis signed an agreement with the papacy giving them and their partners the sole right to mine alum and sell it abroad.
Hibbert wrote, “the French historian, Philippe de Commines, described the bankâ¦as the greatest commercial house that had ever been anywhere. âThe Medici name gave their servants and agents so much credit,' Commines wrote, âthat what I have seen in Flanders and England almost passes belief.'”
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By the 1450s, Florence had silk and food. The Medicis had derived unprecedented riches from the silk trade and had used their wealth to fund astronomers, mathematicians, engineers, sculptors, artists, explorers, cartographers, historians, librarians, archaeologists, and geographers. The Renaissance was in full floodâthanks in part to Chinese inventions and plantsâuse of machines powered by wind and water, Chinese rice, mulberry trees, and silkworms.
O
n New Year's Day 1991, it was savagely cold in Beijing. Marcella and I had spent the night watching sensuous Tang dynasty dancers in their shimmering peacock-blue dressesâa memorable display. I had a bad headache, for obvious reasons, and found the cold that froze my nostrils a pleasant sensation. In those days there were few cars; Beijing streets were a tangled mass of bicycles, their riders swathed in baggy blue jackets and head scarves angled against the biting wind. The treesâstubby pines for the most partâstooped before the wind and glinted with ice crystals. We drove to the southwest of Beijing to board a huge military aircraft that would take us down to Xian.
By the time we took off, the sun was rising in the east, sparkling on the frozen Grand Canal. We flew south over the silver pencil of the canal on our way down to the Yellow River, then turned to the southwest above the river to Xian.
What a prodigious undertaking this Grand Canal wasâdug, according to popular fable, “by a million people with teaspoons.” That is probably a serious underestimate: the workforce is likely to have been nearer five million. Like the Great Wall, the Grand Canal is the result of the obsession of many emperors over thousands of years. They dug in sections, gradually extending, deepening, and widening the canal so that it now links the rice lands of the south with Beijing via the Yangtze, Huang He, and Yellow Rivers.
The canal was started nearly 2,500 years ago and greatly extended during the Sui dynasty (
A.D.
581â618),
1
when Emperor Yang enslaved his people to link his new capital of Luoyang to Xian (in those days called Changan).
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Over two decades, he extended the canal down to Hangzhou, enabling Yangtze junks to travel up the canal to ports along the Yellow River. The canal crossed major rivers, traveling from the Tibetan highlands to the sea.
By the Tang dynasty (
A.D.
618â907), 100,000 tons of grain were transported northward each year. Kublai Khan extended the canal to Beijing in the north and built a number of locksâthere are more than thirty todayârising to 130 feet above sea level.
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Marco Polo was much impressed by the flat canal barges being towed by horses: “This magnificent work is deserving of admiration and not so much from the manner in which it is conducted through the country, or its vast extent, as from its utility and the benefit it produces to those cities which lie on its course.”
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Crossing so many rivers, particularly the Yellow, entailed major engineering challenges. The water level varied enormously depending on the time of year and the amount of snow that had melted in the mountains of Tibet and was carried down the rivers to the sea. Other difficulties arose with the need to carry ships uphill as they neared Beijing. In
The Genius of China,
Robert Temple outlines the problem and the response:
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The canal pound lock was invented in China in 984
A.D.
The inventor was Ch'iao Wei-Yo, who in 983 was appointed Assistant Commissioner of Transport for Huainan. The impetus for his invention was concern over the enormous amounts of grain which were being stolen during canal transport at that time. Grain was the normal tax payment throughout China's history. Movement of the grain to central repositories and warehouses was the lifeblood of the Empire, and any substantial interruption of this process was a very serious social and political problem.
Until 984, boats could only move between lower and higher water levels in canals over double slipways. Chinese boats had no keels and were nearly flat-bottomed. A form of portage had been developed in China, therefore,
whereby spillways originally designed to regulate water flow were elongated in gentle ramps both front and back, leading into the water. A boat would come along and be attached to ropes turned by ox-powered capstans. Within two or three minutes, the boat would be hauled up a ramp to the higher level and for a moment would balance precariously in the air. Then it would shoot forward like an arrow out of a bow and scud along the canal to a level several feet higher than it had started. Passengers and crew had to lash themselves tightly to the boat to avoid being hurled into the air and injured. The great disadvantage of this ingenious technique was that boats often split apart or were seriously damaged by the wear and tear of being dragged up the stone ramps. Whenever a boat broke up on a ramp, the contents would promptly be stolen by organised gangsâincluding corrupt officialsâwho waited for just such an occurrence. Sometimes apparently the ships were roughly handled on purpose, or were artificially weakened or had even been chosen for their weaknesses so that an “accident” of this kind could be brought about intentionally.
Ch'iao Wei-Yo determined to wipe out this practice. He therefore invented the pound lock so that double slipways would not be needed. Here is how the official history of the time relates the story: “Ch'iao Wei-Yo therefore first ordered the construction of two gates at the third dam along the west river (near Huai-Yin). The distance between the two gates was rather more than fifty paces [250 feet], and the whole space was covered over with a great roof like a shed. The gates were hanging gates: when they were closed the water accumulated like a tide until the required level was reached, and then when the time came it was allowed to flow out. He also built a horizontal bridge between the banks and added dykes of earth with stone revetments to protect their foundations. After this was done to all the double slipways the previous corruption was completely eliminated, and the passage of the boats went on without the slightest impediment.”
Pound locks made true summit canals possible. Water levels could differ by four of five feet at each lock without any problems at all. Over a stretch of territory, therefore, a canal could rise more than one hundred feet above sea level, as was the case with the Grand Canal, for instance (rising 138 feet above sea level). This made possible a vast extension of the canal network and freed hydraulic engineers from many awkward topographical restrictions.
The pound locks also conserved water, as Shen Kua relates in
Dream Pool Essays
of 1086:
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It was found that the work of five hundred labourers was saved each year, and miscellaneous expenditure amounting to one million two hundred and fifty thousand cash as well. With the old method of hauling the boats over, burdens of not more than twenty-one tons of rice per vessel could be transported, but after the double gates were completed, boats carrying twenty-eight tons were brought into use, and later on the cargo weights increased more and more. Nowadays [circa 1086] government boats carry up to forty-nine tons and private boats as much as eight hundred bags weighing one hundred and thirteen tons.
Not surprisingly, the
Nung Shu,
the Chinese agricultural treatise published in 1313, illustrated Chinese lock and sluice gates, which were essential to irrigating rice fields and controlling the water levels in canals. Needham states:
There is no doubt that throughout Chinese history the most typical form of sluice and lock gate was what is called the stop-log gateâ¦two vertical grooves fashioned in wood or stone face each other across the waterway, and in them slide a series of logs or baulks let down or withdrawn as desired by ropes attached to each end. Windlasses or pulleys in wood or stone mountings like cranes on each bank helped to fit or remove the gate planks. This system was sometimes improved by fastening all baulks together to form a continuous surface and then raising or lowering it in the grooves by means of boltsâ¦.
The oldest illustration of this kind we have found is in the
Nung Shu
Ch. 18, p 4b, the date of which (+1313) deprives Jacopo Mariano Taccola of the honour of having been the first to illustrate a dam with a sluice gate.
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So by the time Zheng He's junks visited Venice in 1434 the Chinese had hundreds of years' experience in building canals and locks and operating them in all kinds of conditionsâdried-up rivers in summer and torrents in spring.
Lombardy
The geography and climate of Lombardy, the region between the foothills of the Alps and the River Po, resembles that of eastern China. The Po carries melted snow from the great lakes, especially Lake Maggiore, first southward, then east across the flat plain to the Po delta south of Venice. For centuries, the river has provided a means of transporting goods, including wood and marble, from the mountains to the cities of the plains, and her waters have produced fertile land.
Canals have played an important role in the development of commerce, agriculture, and industry in Lombardy. The impetus for Lombardy's first major canal appears to have been the capture of Milan by the Holy Roman Emperor Barbarossa in 1161.
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Milan built substantial defenses, collecting water from local streams to form wide moats around the city. Milan also needed a secure supply of drinking water, and the best available was the River Ticino, which flowed from Lake Maggiore into the Po sixteen miles from Milan. This led to the first canal linking the Ticino with Milanâa huge undertaking for Europeans. The work was completed in about 1180, long before the Chinese arrived in 1434.
The largest canal of this system was called the Naviglio Grande (Grand Canal). It was small, of varying depth, depending on the amount of water coming from the mountains. It had no locks and therefore navigation was hazardous and seasonal. All of this was revolutionized around the year 1450.
This time, the impetus came from Francesco Sforza, a determined and clever leader who seized the throne from Filippo Visconti on his death in 1447. Sforza cut the Naviglio Grande, which promptly deprived Milan of its drinking water. Moreover, the mills alongside the canal lost their power supply so they could no longer grind grain. Milan capitulated and Francesco entered the city as conqueror in 1450. He was proclaimed Duke and created the house of Sforza.
Sforza set about providing Milan with continuous supplies of drinking water, hydropower, and the ability to transfer goods and food throughout
the year. Sforza had inherited a canal in the west that connected Milan to Lake Maggiore, but it had no locks and depended on the variable height of water from the mountains. It was useless for navigation. He decided to equip it with locks and transform it into an all-season, all-weather canal.
He planned to build the Bereguardo Canal in the south, in order to link Milan with Pavia, and in the north a link between Milan and the River Adda, which flowed out of Lake Como. This grand scheme would create a waterway from Lake Maggiore in the west all the way to Lake Como in the east, which could provide water for Milan and serve as a navigation system linking the Adriatic with Lombardy. The problem, of course, was that in 1452 when the plan was conceived, Italians had no method of building locks. Without locks, canals could not functionâespecially not the Bereguardo Canal, which had a fall of eighty-two feet and spring weather that brought melted snow in abundance down from the mountains.
There are no prizes for guessing who provided the design for the locks: it was our old friends, Taccola,
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Francesco di Giorgio, and Leon Battista Alberti. Francesco, as described in chapter 16, copied and improved upon Taccola's work. We presume he, like Taccola, had access to and copied from the
Nung Shu
. In chapter 16 we described di Giorgio's
Trattato di Architettura,
notably the copy marked Codex Laurenziano, which was owned by Leonardo da Vinci and is now found in the Laurenzian Library in Florence. Also deposited with that document is di Giorgio's
Trattato dei Pondi Leve e Tirari
.
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One of the last descriptions in the Laurenziana Codex, no. 361, concerns a series of lock gates:
If along a riverâ¦. we wish to conduct boats, when due to little water and an incline it might be impossible to navigate, it is necessary to determine the fallâ¦. Let us suppose that the first part of the river has a drop of thirty piede: construct at that point a high door in the manner of a portcullisâ¦. with windlasses to raise it, and in this manner lay off the entire length of the river and all its falls with such doors. After the boat enters, and the door is closed, the boat will soon riseâ¦and will be able to enter the second chamberâ¦and so step by step you will be able to take the boat to wherever you wish. Should you desire to return down, by opening each door, the boat with the water will be led to the next door, and so from one to the other it will be
possible to return to the sea. All boats should be made with flat bottoms, so that they will float on little water.
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This description is accompanied by a picture showing a lock system with no fewer than four locks. The date of the picture, from the Hans Lee Laurenziana Codex,
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is about 1450âa date fixed by the description of the destruction of central Ragusa (Dubrovnik).
Sforza and his architect, Bertola de Novale, now had illustrations of how to build locks. At first they found them puzzling. Here is William Parsons's
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description: “But the details of the locks were not understood and the contractors refused to move. So Berenzo de Passaro wrote further urgent requests to the Duke to send Bertola with the necessary explanations.”
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Parsons continues:
By 1461 the canal was completed as is shown by another letter by Lorenzo, in which he complains of defects in the locks and asks again that Bertola be sent to remedy the troubles. In this letter he writes of the locks being two
braccia
deeper than the bottom of the canal [which must refer to the height of fall]. The defects were said to be in the gates: their hinges were weak and the gates themselves could not withstand the water pressure.
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