One unpublished manuscript "Inductive Heating Without Transformer Iron," 1925-1928. A complete set of Northrup's writings is available, although in printed form, and with no manuscripts leading to publication of these papers. There are two photographs of Northrup and a scrap book of early photographs of test equipment, including one of Northrup and his associates at the time of the invention of the induction furnace. Also available is biographical material including an obituary.