Linda Derry raises a good point about determining whether or not a feature
was intended as a privy.  Most are readily identifiable through odor, but 
in some cases, such as the deep shaft features common in Philadlphia, the 
feature form and construction may resemble wells.  A few years ago, while 
working on an urban site from the turn of this century in Paterson, NJ, we
encountered several square and rectangular features containing dark,
artifact-rich fill,  We initially felt that they were privies due to the
resemblance to the rectilinear wooden box privies that we were finding, and
when they turned out to be a foot or so deep, we decided that they were
privies that were abandoned for some reason before completion.  Later
discussions with Marley Brown indicated that they might have been garden
beds, a more likely explanation.
 
L. J. Cook