My thanks to all the helpful responses to my question about Leffel
and Parker wheels.  I spent an informative two days last week on back
issues of Old Mill News, and working my way through Louis Hunter, and will be
checking out other sources that I found on my e-mail today.  I found an
interesting, highly readable (as opposed to Oliver Evans who is a bit of a
tough study) source by John Storck and Walter Dorwin Teague called
Flour for Man's Bread (1952 University of Minnesota Press, Minneapolis) that
is good for the history of milling, and gives useful tips on how to determine
the rate of flow of a stream so you can figure out what its "head" should be,
as well as extraction rates for wheat (percentage of the wheat that actually
becomes usable flour) and other enlightening bits of information.  It has
made me ponder my sandwiches in a whole new light.  Now if I could just find
a practical guide to retroactively building a mill in a specific spot...(like
when you have the mill building foundation, and can measure the wheel pit, but
don't know where the dam(s) were; as is my current dilemma).  There seems to
be lots of factors ranging from the amount of capital available for investment
to the type of wheel to be used to the quality of the waterflow.  However,
every mill site I have seen is more or less unique in that the layout of the
dam and its relationship to the mill siting is customized to the topography
and local physical situation.  Some sites are easy to figure out and some are
downright mysterious.  But it is all fascinating (to me at least).
Thanks again for the references.