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 researching this topic I looked into the history of salted paper maps and found several examples by Talbot as well as information regarding it's extensive use by the English Ordnance Survey under the direction of Henry James in the 1850's. A wonderful publication in the collection of the Geography and Maps Division at the Library of Congress shows the results of an Ordnance Survey review committee tasked with determining the accuracy and reliability of photography for the reduction of maps. This copy has several photographs of the facilities and examples of maps as well as hand colored engravings of the darkroom equipment. This image is of the darkroom facilities and map mounting workshop.
I would be interested in knowing if anyone in the UK has done research in this area or if anyone knows where the archival papers and documentation of the Ordnance Survey is held. (These salted paper maps were only done as internal copies and were not available for sale or distribution.)
A brief overview of this research can be read at: Heliographic Musings
Image: Photographic Headquarters, English Ordnance Survey, from The Report of the Committee on the Reduction of Ordnance Plans by Photography, 1859.
