On Thu, 16 Oct 2008 13:57:44 -0700, Jeff Liebermann
wrote:

Worse, the back pressure created by the
immovable column of sand will force some sand particles into the
conduit around the edges with the "reflected" air pressure.

H E R E S Y

Reflected waves do NOT have power in them - or so goes the catechism.

This new and dangerous introduction of a side topic can only lead to
endless debate about the superposition phase properties of sand in
vacua (particel theories inhabiting the crevices in the science of
Equal Librium)

73's
Richard Clark, KB7QHC