I have just got on to the Armstrong list and seen some of your writings on the furances of the area. I may recommend the aerial photos in the National Archives cartography section for purchase since they date from the mid 1930's and still show many details now since gone. Most of the photos were taken in the winter or early spring for mapping purposes. They cost $10-15 each for a 10" x 10" photo and are easy to order if your have the roll and frame numbers. I have a few and they are fun to use if you are going hunting on the ground. Also for history, since the furnaces were an extraction industry the US Geological Survery library in Reston Virginia and I assume the Pennsylvania Geo Survey in Harrisburg have good "old books" on the furnaces written from a "rocks" perspective but which many times contain names of people as owners or operators. I've used their fcailities to research the old Red Bank Furnace by Thomas McCullough and found many interesting itmes. All this is FYI Brian Green sangreen@tmn.com