William A. Gordon wrote:

>For those who plan to pursue further study of drainage and sewer pipes,
>I learned today that there is/was a "Clay Sewer Pipe Association" while
>surfing at ebay.

Pipes (and drain tiles) are an artifact we all can expect to encounter, and
there is quite a literature. One of my favorite basic books was written as
a promotion for cast-iron water pipes:

R. C. McWane

1917     Pipe and the Public Welfare
         The Stirling Press, New York.

Ignore (or perhaps interpret) some of the cast-iron polemics, and this book
has some really good tidbits. I use it frequently, keeping in mind the
obvious bias of the author, who was dead set against using wood for water
pipes.

      _____
 ____(_____)__          What's the difference between an
  |Baby the\            archives and a landfill?
  |1969 Land\_|===|_
  |  ___Rover   ___ |o                          seagulls
  |_/ . \______/ . ||
  ___\_/________\_/____________________________________________
  Ned Heite, Camden, DE  http://home.dmv.com/~eheite/index.html