[Aztlan] Inca suspension bridges and good summer reads

Mon May 14 13:54:30 CDT 2007

Thank you very much for raising this point about the Inca video "Secrets of Lost Empires: Inca."  I also use it in my courses, and it is very good.

  The video also accentuates the point made by Bill Conklin that the Incas were indeed a textile-oriented society, and this carried over into bridge making, roof building, khipu recording, textile weaving, shoe making, and everything else.

  Another excellent video I would highly recommend if you teach Inca history, Andean archaeology, or colonial chronicles courses is "Inca: Secrets of the Ancestors" (part of the Time/Life "Lost Civilizations" series).  This video highlights the point that the Inca civilization marked the culmination of thousands of years of cultural development in the Andes. 

  Yet one more book I would like to add to your wonderful summer reading list is Whispering in the Giant's Ear: A Frontline Chronicle from Bolivia's War on Globalization by William Powers.  This is a memoir of a development aid worker who worked among the Chiquitano Indians of the Bolivian Amazon.  This book is a very engaging narrative, but also a very astute observation of the nuances of a changing Amazonian culture, and the various internal and external influences that impact its development.  Powers adopts a non-traditional view of development as "green globalization" -- the potential for ecologically rich but economically poor nations to develop its economy through ecologically friendly activities, such as ecotourism, ethnotourism, carbon ranching, and so forth.  

  Saludos a todos,

  Margarita Marin-Dale
  American University

"Diehl, Richard" <rdiehl at as.ua.edu> wrote:
  Hola Listeros,

I am somewhat surprised to see that nobody has mentioned an outstanding
video on building Inca bridges. It was done about 10 years ago as part
of the BBC/NOVA/PBS series SECRETS OF LOST EMPIRES and carried the
sub-title INCA. It contains lots of good ideas and experiments,
including an actual re-building by members of the local community of the
only suspension bridge currently in use. I use it in class all the time.
For one thing, it shows how important the social factors are in
constructing and maintaining such structures.

Secondly, for those who are looking for fun things to read over the
summer, I have three suggestions. FINAL REPORT by Michael D. Coe and
NEVER IN FEAR by Merle Greene Robertson are both autobiographies by
outstanding scholars who happen to be excellent writers. Both are richly
illustrated, especially Merle's, including some of her gorgeous water
colors. Finally, for anyone interested in general field science and
Amazonia, I cannot rave enough about LAND OF GHOSTS: THE BRAIDED LIVES
OF PEOPLE AND THE FOREST IN WESTERN AMAZONIA by botanist David G.
Campbell. I have bee doing a lot of reading on the Amazon in the last
nine months for a course I just finished teaching and they don't get any
better than this. Indispensable things to take to the airport or the
beach!

Saludos,
Dick Diehl

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Today's Topics:

1. INCA SUSPENSION BRIDGES (michael ruggeri)
2. Suspension Bridges of the Americas (Elaine Day Schele)
3. Suspension Bridges of the Americas (Jorge P?rez de Lara)

----------------------------------------------------------------------

Message: 1
Date: Tue, 8 May 2007 06:30:15 -0500
From: michael ruggeri 
Subject: [Aztlan] INCA SUSPENSION BRIDGES
To: Aztlan 
Message-ID: 
Content-Type: text/plain; charset=WINDOWS-1252; delsp=yes;
format=flowed

How the Inca Leapt Canyons

By JOHN NOBLE WILFORD
Published: May 8, 2007
CAMBRIDGE, Mass. ? Conquistadors from Spain came, they saw and they 
were astonished. They had never seen anything in Europe like the 
bridges of Peru. Chroniclers wrote that the Spanish soldiers stood in 
awe and fear before the spans of braided fiber cables suspended 
across deep gorges in the Andes, narrow walkways sagging and swaying 
and looking so frail.

Yet the suspension bridges were familiar and vital links in the vast 
empire of the Inca, as they had been to Andean cultures for hundreds 
of years before the arrival of the Spanish in 1532. The people had 
not developed the stone arch or wheeled vehicles, but they were 
accomplished in the use of natural fibers for textiles, boats, sling 
weapons ? even keeping inventories by a prewriting system of knots.

So bridges made of fiber ropes, some as thick as a man?s torso, were 
the technological solution to the problem of road building in rugged 
terrain. By some estimates, at least 200 such suspension bridges 
spanned river gorges in the 16th century. One of the last of these, 
over the Apurimac River, inspired Thornton Wilder?s novel ?The Bridge 
of San Luis Rey.?

Although scholars have studied the Inca road system?s importance in 
forging and controlling the pre-Columbian empire, John A.Ochsendorf 
of the Massachusetts Institute of Technology here said, ?Historians 
and archaeologists have neglected the role of bridges.?

Dr. Ochsendorf?s research on Inca suspension bridges, begun while he 
was an undergraduate at Cornell University, illustrates an 
engineering university?s approach to archaeology, combining materials 
science and experimentation with the traditional fieldwork of 
observing and dating artifacts. Other universities conduct research 
in archaeological materials, but it has long been a specialty at M.I.T.

Students here are introduced to the multidisciplinary investigation 
of ancient technologies as applied in transforming resources into 
cultural hallmarks from household pottery to grand pyramids. In a 
course called ?materials in human experience,? students are making a 
60-foot-long fiber bridge in the Peruvian style. On Saturday, they 
plan to stretch the bridge across a dry basin between two campus 
buildings.

In recent years, M.I.T. archaeologists and scientists have joined 
forces in studies of early Peruvian ceramics, balsa rafts and metal 
alloys; Egyptian glass and Roman concrete; and also the casting of 
bronze bells in Mexico. They discovered that Ecuadoreans, traveling 
by sea, introduced metallurgy to western Mexico. They even found how 
Mexicans added bits of morning-glory plants, which contain sulfur, in 
processing natural rubber into bouncing balls.

?Mexicans discovered vulcanization 3,500 years before Goodyear,? said 
Dorothy Hosler, an M.I.T. professor of archaeology and ancient 
technology. ?The Spanish had never seen anything that bounced like 
the rubber balls of Mexico.?

Heather Lechtman, an archaeologist of ancient technology who helped 
develop the M.I.T. program, said that in learning ?how objects were 
made, what they were made of and how they were used, we see people 
making decisions at various stages, and the choices involve 
engineering as well as culture.?

>From this perspective, she said, the choices are not always based 
only on what works well, but also are guided by ideological and 
aesthetic criteria. In the casting of early Mexican bells, attention 
was given to their ringing tone and their color; an unusually large 
amount of arsenic was added to copper to make the bronze shine like 
silver.

?If people use materials in different ways in different societies, 
that tells you something about those people,? Professor Lechtman said.

In the case of the Peruvian bridges, the builders relied on a 
technology well suited to the problem and their resources. The 
Spanish themselves demonstrated how appropriate the Peruvian 
technique was.

Dr. Ochsendorf, a specialist in early architecture and engineering, 
said the colonial government tried many times to erect European arch 
bridges across the canyons, and each attempt ended in fiasco until 
iron and steel were applied to bridge building. The Peruvians, 
knowing nothing of the arch or iron metallurgy, instead relied on 
what they knew best, fibers from cotton, grasses and saplings, and 
llama and alpaca wool.

The Inca suspension bridges achieved clear spans of at least 150 
feet, probably much greater. This was a longer span than any European 
masonry bridges at the time. The longest Roman bridge in Spain had a 
maximum span between supports of 95 feet. And none of these European 
bridges had to stretch across deep canyons.

The Peruvians apparently invented their fiber bridges independently 
of outside influences, Dr. Ochsendorf said, but these bridges were 
neither the first of their kind in the world nor the inspiration for 
the modern suspension bridge like the George Washington and Verrazano- 
Narrows Bridges in New York and the Golden Gate in San Francisco.

In a recent research paper, Dr. Ochsendorf wrote: ?The Inca were the 
only ancient American civilization to develop suspension bridges. 
Similar bridges existed in other mountainous regions of the world, 
most notably in the Himalayas and in ancient China, where iron chain 
suspension bridges existed in the third century B.C.?

The first of the modern versions was erected in Britain in the late 
18th century, the beginning of the Industrial Revolution. The longest 
one today connects two islands in Japan, with a span of more than 
6,000 feet from tower to supporting tower. These bridges are really 
?hanging roadways,? Dr. Ochsendorf said, to provide a fairly level 
surface for wheeled traffic.

In his authoritative 1984 book, ?The Inka Road System,? John Hyslop, 
who was an official of the Institute of Andean Research and 
associated with the American Museum of Natural History, compiled 
descriptions of the Inca bridges recorded by early travelers.

Garcilasco de la Vega, in 1604, reported on the cable-making 
techniques. The fibers, he wrote, were braided into ropes of the 
length necessary for the bridge. Three of these ropes were woven 
together to make a larger rope, and three of them were again braided 
to make a still larger rope, and so on. The thick cables were pulled 
across the river with small ropes and attached to stone abutments on 
each side.

Three of the big cables served as the floor of the bridge, which 
often was at least four to five feet wide, and two others served as 
handrails. Pieces of wood were tied to the cable floor. Finally, the 
floor was strewn with branches to give firm footing for beasts of 
burden.

More branches and pieces of wood were strung to make walls along the 
entire length of the bridge. The side covering, one chronicler said, 
was such that ?if a horse fell on all fours, it could not fall off 
the bridge.?

Still, it took a while for the Spanish to adjust to the bridges and 
to coax their horses to cross them. The bridges trembled underfoot 
and swayed dangerously in stiff winds.

Ephraim G. Squier, a visitor to Peru from the United States in the 
1870s, said of the Apurimac River bridge: ?It is usual for the 
traveler to time his day?s journey so as to reach the bridge in the 
morning, before the strong wind sets in; for, during the greater part 
of the day, it sweeps up the Canyon of the Apurimac with great force, 
and then the bridge sways like a gigantic hammock, and crossing is 
next to impossible.?

Other travelers noted that in many cases, two suspension bridges 
stood side by side. Some said that one was for the lords and gentry, 
the other for commoners; or one for men, the other for women.

Recent scholars have suggested that it was more likely that one 
bridge served as a backup for the other, considering the need for 
frequent repairs of frayed and worn ropes.

The last existing Inca suspension bridge, at Huinchiri, near Cuzco, 
is virtually rebuilt each year. People from the villages on either 
side hold a three-day festival and gather stiff grasses for producing 
more than 50,000 feet of cord. Finally, the cord is braided into 150- 
foot replacement cables.

In the M.I.T. class project, 14 students met two evenings a week and 
occasional afternoons to braid the ropes for a Peruvian bridge 
replica 60 feet long and 2 feet wide. They were allowed one important 
shortcut: some 50 miles of twine already prepared from sisal, a 
stronger fiber than the materials used by the Inca.

Some of the time thus gained was invested in steps the Inca had never 
thought of. The twine and the completed ropes were submitted to 
stress tests, load-bearing measurements and X-rays.

?We have proof-tested the stuff at every step as we go along,? said 
Linn W. Hobbs, a materials science professor and one of the principal 
teachers of the course.

The students incorporated 12 strands of twine for each primary rope. 
Then three of these 12-ply ropes were braided into the major cables, 
each 120 feet long ? 60 feet for the span and 30 feet at each end for 
tying the bridge to concrete anchors.

One afternoon last week, several of the students stretched ropes down 
a long corridor, braiding one of the main cables. While one student 
knelt to make the braid and three students down the line did some 
nimble footwork to keep the separate ropes from entangling, Zack 
Jackowski, a sophomore, put a foot firmly down on the just-completed 
braid.

?It?s important to get the braids as tight as possible,? Mr. 
Jackowski said. ?A little twist, pull it back hard, hold the twist 
you just put in.?

No doubt the students will escape the fate of Brother Juniper, the 
Franciscan missionary in Wilder?s novel who investigated the five 
people who perished in the collapse of the bridge of San Luis Rey.

Brother Juniper hoped to discern scientific evidence of divine 
intervention in human affairs, examples of ?the wicked visited by 
destruction and the good called early to Heaven.?

Alas, he could not; there is some of both good and evil in people. So 
his written account was judged heretical. He and his manuscript were 
burned at the stake.

If the students? bridge holds, they will have learned one lesson: 
engineering, in antiquity as now, is the process of finding a way 
through and over the challenges of environment and culture.

Mike Ruggeri's Ancient America and Mesoamerica News and Links
http://community-2.webtv.net/Topiltzin-2091/MIKERUGGERISANCIENT/ 
index.html

Mike Ruggeri's Maya Archaeology News and Links
http://community-2.webtv.net/Topiltzin-2091/MIkeRuggerisMaya/index.html

Mike Ruggeri's Ancient America Museum Exhibitions, Conferences and 
Lectures
http://community-2.webtv.net/Topiltzin-2091/AncientAmerica/index.html

Mike Ruggeri's Mound
Builders and Ancient Southwest News and Links
http://community-2.webtv.net/Topiltzin-2091/MIKERUGGERISMOUND/index.html

Mike Ruggeri's Andean Archaeology News and Links
http://community-2.webtv.net/Topiltzin-2091/MikeRuggerisAndean/ 
index.html

------------------------------

Message: 2
Date: Tue, 8 May 2007 07:41:23 -0500
From: "Elaine Day Schele" 
Subject: [Aztlan] Suspension Bridges of the Americas
To: "Aztlan" 
Message-ID: <000c01c7916e$3036db40$6401a8c0 at gis>
Content-Type: text/plain; charset="iso-8859-1"

Thank you Michael, for that fascinating article on the Inca bridges and
the experimental archaeology being conducted by the scholars of MIT. My
best wishes for a successful outcome. Looks like a swinging time is in
store for all .

I have what I think is a correction to the writer's statement of
suspension bridges where he writes "The Inca were the only ancient
American civilization to develop suspension bridges." 

There is also evidence that the Maya also used suspension bridges,
although not across canyons, but across the Usumacinta at Yaxchilan
(perhaps other places yet unknown), which means that it was a
combination of rope suspension and pier suspension. See the following
article where engineer was applied to archaeology to come up with a
computer model. http://gtalumni.org/news/ttopics/win97/bridge.html. 

For the Maya, ropes and cords were symbolic of the "sky umbilicus", and
the bridge may also have had spiritual meaning in addition to economic
importance.

Elaine

------------------------------

Message: 3
Date: Tue, 08 May 2007 10:09:00 -0500
From: Jorge P?rez de Lara 
Subject: [Aztlan] Suspension Bridges of the Americas
To: Aztlan 
Message-ID: <4640928C.6070506 at estudioelias.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Listeros,

As much as one likes to think that the civilization which is the object 
of our studies (in this case, the Maya) developed independently the 
concept of large suspension bridges, I feel one should be cautios about 
the drawing of any conclusions: a possible Usumacinta suspension bridge 
at Yaxchil?n is merely a plausible idea for which, alas!, very little 
actual evidence exists. The fact that something is possible does not 
necessarily prove that that something ever existed. The fact that there 
were no attestations of suspension bridges of any substance among the 
Maya (or, indeed, Mesoamerica) by the Spaniards should give one pause 
before promoting an idea to reality.

Jorge Perez de Lara

Elaine Day Schele wrote:

>Thank you Michael, for that fascinating article on the Inca bridges and
the experimental archaeology being conducted by the scholars of MIT. My
best wishes for a successful outcome. Looks like a swinging time is in
store for all .
>
>I have what I think is a correction to the writer's statement of
suspension bridges where he writes "The Inca were the only ancient
American civilization to develop suspension bridges." 
>
>There is also evidence that the Maya also used suspension bridges,
although not across canyons, but across the Usumacinta at Yaxchilan
(perhaps other places yet unknown), which means that it was a
combination of rope suspension and pier suspension. See the following
article where engineer was applied to archaeology to come up with a
computer model. http://gtalumni.org/news/ttopics/win97/bridge.html. 
>
>For the Maya, ropes and cords were symbolic of the "sky umbilicus", and
the bridge may also have had spiritual meaning in addition to economic
importance.
>
>Elaine
>_______________________________________________
>Aztlan mailing list
>Aztlan at lists.famsi.org
>http://www.famsi.org/mailman/listinfo/aztlan
>
>
> 
>

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