Share 'Map Reproductions in Salted Paper by the English Ordnance Survey'

I have been researching a Civil War map reproduction technique involving the photographing or direct copying of maps using the salted paper process.  These maps were fairly common in the United States during the Civil War due to the limited availability of lithographic presses as well as the increased demand for up-to-date maps of strategic sites such as waterways, railroads, etc.  While researc…