This folder contains correspondence relating to the technical and commercial development of Portland cement. Included are comments by Edison about the durability of his concrete buildings during the fire of December 9, 1914, that destroyed or damaged more than half of the buildings in the West Orange laboratory complex. A letter from civil engineer Nathan C. Johnson contains a lengthy comment by Edison about the value of microscopic inspection for studying cement.
Approximately 20 percent of the documents have been selected. Letters that received no reply or only a perfunctory response from Edison have not been selected. Also not selected are monthly financial reports from the Edison Portland Cement Co. Courtesy of Thomas Edison National Historical Park.