You should also check the following comprehensive reference on this subject:
 
Roenke, Karl G.
  1978  Flat Glass: Its Use as a Dating Tool for Nineteenth Century
     Archaeological Sites in the Pacific Northwest and Elsewhere.
      Northwest  Anthropological Research Notes, Memoir No. 4.
     (University of Idaho, Moscow series).
 
This was a thesis done by this person which was published in this series
which should be available in any good research library.
 
Mike Polk