In John McPhee's book _The Pine Barrens_ he talks about the
movement of iron in the boggy soil. In one whopper of a sentence,
he says, "One of the geological curiousities of the Pine Barrens
is that rain-water soaking down through the fallen pine needles
and other forest litter takes on enough acid to leach out iron
from the sands below; the dissolved iron moves underground into
the streams, where it oxidizes on contact with the air and forms
a patch of scum on the surface that is partly rust brown and
partly iridescent blue, and resembles an oil slick left by an
outboard motor; drifting over to the edges of the streams, this
iron-oxide film permeates the sands and gravels of the riverbanks
and cements them together into a sandstone composite that has
been known for centuries as bog iron." (p 27) He also says on p16
that "Sea captains once took the cedar waters of the Pine Barrens
rivers with them on voyages, because cedar water would remain
sweet and potable longer than any other water they could find."
A good book from a good author despite the wordy style.
Phil