[Aztlan] Fw: Reply to Aztlan Digest, Vol 18, Issue 8. On Suspension Bridges, esp. one at Yaxchilan

[Ronald.L.Canter at faa.gov]

Reply to Aztlan Digest, Vol 18, Issue 8.

Suspension Bridge at Yaxchilan

      After spending a little time studying the waterfront at Yaxchilan
locating stones grooved by long use as moorings, I also looked at the Maya
suspension bridge proposed by James O'Kon.  Though a very appealing
concept, I have to say that I am not convinced.  The suggested bridge lines
up well horizontally with the hieroglyphic staircase in the Main Plaza, but
there are problems with the vertical lineup.
      The staircase leads to the top of Structure 5, which is 22 meters
above average low water stage.  This is on river-left, the city side.  On
river-right, the Guatemalan side, the river terrace level is much lower,
12.6 meters above low water.  There should be the remains of an approach
ramp and a sturdy anchoring structure 10 meters high on the Guatemalan
side, but there is nothing.  The floor of the bridge would have been at the
height of Structure 5, not only to connect but also to rise well above the
normal bankfull stage, which is not coincidentally 12.6 meters above low
water.  Since the bridge floor would have gone through (not on top of)
them, support towers would need to be at least 28 meters high - on a 10
meter base (the width of El Pilar).  Such tall, thin towers are very
unusual in Maya architecture, and unprecedented for ones placed right in a
swift river.
      This does not mean the proposed suspension bridge was impossible,
just that the parts don't seem to fit well.
Ron Canter