Have the effects of a solar eclipse on a Foucault's Pendulum (where
the rate of the apparent rotation of the pendulum swing is increased
during the eclipse) ever been diffinitively proven (or disproven)?
Thanks!

Allais Effect on Foucault's Pendulum 
 
 Question:
 The mystery lies in the question: Does a solar eclipse somehow affect
a Foucault pendulum? In 1954, Maurice Allais reported that a Foucault
pendulum exhibited peculiar movements at the time of a solar eclipse.
If true, his finding raises new questions about the nature of such
phenomena.
 http://science.nasa.gov/newhome/headlines/ast06aug99_1.htm
 
 answer: not known as of 1999
 
 Results of August 11 eclipse will have to be coordinated with lunar
opposition (2 weeks later) before a first summary of eclipse data will
be available. Realistically, scientists think it will take at least a
decade before all opinions are settled.
 
 

NASA/Marshall scientists will probe an unlikely 50-year old mystery 
during the August 11, 1999 total solar eclipse
http://ams.astro.univie.ac.at/~nendwich/Science/SoFi/allais2.html

http://sunearth.gsfc.nasa.gov/edreferr.htm


As of 2003 :  It as an optical effect casued by air movement above the cloud level
              Nothing to do with gravity 

(technical paper in PEER REVIEWED journal)
http://www.eclipse2006.boun.edu.tr/sss/paper01.pdf

"It as an optical effect casued by air movement above the cloud level/
Nothing to do with gravity"

Actually if you read the paper that the link points to it says that
air collects above an observer in the moon's shadow because of the
drop in temperature, increasing the density of the air. The air is
massive enough to produce a noticable gravitational force upwards.
Very much to do with gravity.

A recent review paper on this matter.
http://arxiv.org/ftp/gr-qc/papers/0408/0408023.pdf

It seems that the explanation is spurious at best. The effect is at
least 100,000 times too small to account for the effect. It would seem
that the effect has been replicated enough times to consider it real.
The atmospheric effect does not fit the curve of effects properly
either. The tests were performed indoors, so an optical effect seems
unlikely even if the density of the air did increase.