Workers dragged Forbidden City stones along roads of artificial ice

Nov 05, 2013 by Marcia Malory report
Workers likely slid massive stones, such as this 300-ton marble carving in front of the Hall of Supreme Harmony in the Forbidden City, Beijing, China, along artificial ice paths. Credit: Chui Hu

(Phys.org) —Fifteenth and sixteenth century Chinese workers transported enormous stones to the Forbidden City by carrying them in sledges along roads of artificial ice, according to Jiang Li of the University of Science and Technology in Beijing and his colleagues. The researchers translated a document showing that in 1557, workers used this method to transport a 123-ton stone more than 70 kilometers. Li and his team say that dragging large stones over ice, rather than over dry ground, reduced the amount of friction created and the number of workers needed for the job. The study appears in the Proceedings of the National Academy of Sciences.

Construction of China's Forbidden City, in present-day Beijing, began in 1417. The home of China's emperors for almost 500 years, The Forbidden City incorporates stones weighing more than 100 tons extracted from the Dashiwo quarry, 70 kilometers away. The heaviest of these is the Large Stone Carving, which weighs more than 300 tons.

Previous researchers assumed that the Chinese used wheeled vehicles to move the stones. The Chinese were using wheeled vehicles for transport by around 1500 BC, and there are no images of dragging over dry ground. However, none of the wheeled vehicles built before 1596 could carry more than 95 tons. Although some books mention that workers used an artificial ice path to transport the Large Stone Carving, there are no detailed historical records of this event.

Li and his colleagues translated a Chinese text written in 1618 that describes how workers brought a 123-ton stone to the Forbidden City in 1557, during a mid-winter renovation project. The workers placed the stone on a sledge, which they then dragged along an artificial ice path, created by pouring well water onto the ground and then allowing the water to freeze. They dug wells every half kilometer. By pouring water over ice that had already frozen, they created a liquid surface that decreased the friction between the sledge and the ice. The workers had time to move the sledge across the liquid film before it froze.

The team calculated that it would have taken 1,537 men to drag the load over dry ground. Dragging a sledge over ice would have required 338 men. Lubricating the ice would have reduced the workforce to 46 men. An road also eliminated the need to lay out wooden planks to create a smooth surface.

Architects of the reconstruction debated whether to use sledges or mule-driven wagons. They chose sledges because they were safer and more reliable than wagons, although sledges required more time, money and manpower.

The research suggests that, at the time, Chinese engineers knew more about friction than Western engineers did.

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More information: Ice lubrication for moving heavy stones to the Forbidden City in 15th- and 16th-century China, PNAS, www.pnas.org/content/early/2013/10/30/1309319110

Abstract
Lubrication plays a crucial role in reducing friction for transporting heavy objects, from moving a 60-ton statue in ancient Egypt to relocating a 15,000-ton building in modern society. Although in China spoked wheels appeared ca. 1500 B.C., in the 15th and 16th centuries sliding sledges were still used in transporting huge stones to the Forbidden City in Beijing. We show that an ice lubrication technique of water-lubricated wood-on-ice sliding was used instead of the common ancient approaches, such as wood-on-wood sliding or the use of log rollers. The technique took full advantage of the natural properties of ice, such as sufficient hardness, flatness, and low friction with a water film. This ice-assisted movement is more efficient for such heavy-load and low-speed transportation necessary for the stones of the Forbidden City. The transportation of the huge stones provides an early example of ice lubrication and complements current studies of the high-speed regime relevant to competitive ice sports.

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User comments : 11

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katesisco
1 / 5 (15) Nov 05, 2013
J Needham's books, abbreviated in: The Genius That Was China is a marvel that scarce can be believed.
I suggest this period of 'known things' is only one of many in our past sparked by our sun's equatorial emissions that occur when the magnetic reversal stalls and the sun has two of the same magnetic polarity.
It is not just that our intelligence is greater-- it is that the sun emissions cause atomic structure to be more condensed, more focused, more well built. I proposed that Sol is a magnetar whose center --Sol--- occurred when a red giant collapsed inward. I suggest that the equatorial emissions were constant and degraded to infrequent when the magnetar rapidly aged. These solar equatorial emissions are our 'evolution' and 'mutations.' As these emissions only infrequently and briefly occur now, our insight into cellular, atomic, and sub atomic structure is ephemeral as is the applications gained with this insight.
Flowers for Algernon is a perfect description.
Lurker2358
1.8 / 5 (15) Nov 05, 2013
....But they MUST have had help from the Ancient Aliens, right? Human beings didn't know how to pour water and make ice.

Where'd the humans learn how to dig wells? Huh, huh? There I got ya.

Seriously, another jab at the AA nuts.
Eikka
1.3 / 5 (12) Nov 05, 2013
It's also interesting to note that the temperatures where the pyramids are in Giza drop significantly in the winter months, and fall to freezing during the nights in the desert.

It's possible to create ice there by placing water in a wide pan under the sky at night because there's no cloud coverage which creates the same heat loss effect as what puts frost on car windows. It's unlikely that enough ice could be created and preserved through the daylight to form a road surface though, but one can imagine enough could be accumulated to make a fancy sorbet the next day.

baudrunner
1.2 / 5 (12) Nov 05, 2013
@Lurker, you're not reading, just blabbing. Pouring water and making ice isn't any harder than pouring water and waiting for it to freeze. @katesisco, ice ages happen in cycles. We're talking history based on dating techniques that, if they were accurate, would put this period at a time when it was easy to do this sort of thing.

100 tons is nothing. The very ancients moved stones that weighed in excess of over 1,600 tons over long distances and over difficult terrain. Technologies existed then over which we can only speculate. Google "Schist Disk" to see something that might have very well served as, or was a symbolic facsimile of, a part of a compressor that carved those great blocks of stone using high pressure water jets, for example. Who knows but that those Baalbek stones were moved using the same techniques, since we are not sure about the age of those stone blocks, except that there is some evidence for their having been originally placed there over 25,000 years ago.
baudrunner
1 / 5 (12) Nov 05, 2013
Insightful article, by the way, PO. Thanx.
Meyer
5 / 5 (3) Nov 05, 2013
Um, they used artificial paths of real ice, not roads of artificial ice.
Huns
2.8 / 5 (5) Nov 05, 2013
I suggest this period of 'known things' is only one of many in our past sparked by our sun's equatorial emissions that occur when the magnetic reversal stalls and the sun has two of the same magnetic polarity.

Prove any of this.
Humpty
1.3 / 5 (12) Nov 06, 2013
"The research suggests that, at the time, Chinese engineers knew more about friction than Western engineers did."

No they did not....

They just had particular circumstances, and gave it some thought and came up with a solution.

It's like saying putting a ceramic urn of water out side in a cold night and having it turn to ice and break the urn, makes me an ancient expert on hydraulic fracturing....

Or that blocking a stream, and digging a ditch across the side of the hill, can divert that water sidewards for quite a great distance.....

It's like how fucking stupid....

Even my cat knows how to time door openings and closings and when to dart through....

Macrocompassion
1.6 / 5 (12) Nov 06, 2013
1. When a sledge runner is slid on ice, the low friction is due to very local melting of the ice. pouring water on it was not a necessary nor useful technique.

2. This explanation is good for level ground, but with the need to go up and down hills, the ice solution is not practical. So how did the Chinese negociate hilly roads with 300 tons of rock?
baudrunner
1 / 5 (9) Nov 07, 2013
Macrocompassion: That's the million dollar question that has everybody puzzled. How were large blocks of stone moved in the days when their most sophisticated technologies (we speculate) involved draw horses, manpower, and block and tackle?

In the third century AD, the Romans moved a 300 ton obelisk in one piece from Egypt to Rome, where it stands today in St Peter's square. We know how they did it, because there is a detailed account of it in the archives. However, when you do the math, I doubt that the same means could be used to move those Baalbek stones. They weighed five times as much, and this would require five times the logistical support of that 300 ton obelisk.

My conclusion is that they had help.
praos
1 / 5 (7) Nov 10, 2013
It's also interesting to note that the temperatures where the pyramids are in Giza drop significantly in the winter months, and fall to freezing during the nights in the desert.

It's possible to create ice there by placing water in a wide pan under the sky at night because there's no cloud coverage which creates the same heat loss effect as what puts frost on car windows. It's unlikely that enough ice could be created and preserved through the daylight to form a road surface though, but one can imagine enough could be accumulated to make a fancy sorbet the next day.


Stones could be dragged even during the night, isn't it?

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