Folder containing letters from Milk Marque, Prof. R.H. Ellis, National Institute for Research in Dairying and others to A.S. Cromarty, as well as copies of photographs of Dairy Heat Recovery Unit (HRU) equipment and researchers, schematic diagrams of bulk tanks and HRUs. The file also includes a note by A.S. Cromarty on 'Historical developments' in the field of milk cooling and heat recovery, and several short accounts written by Cromarty of work carried out between the 1950s- 1970s in this area. There are also a few later copies of articles and photos from the 1930s - 1960s, as well as an information sheet from South West Refrigeration: 'Heat Reclaim: The Green Machine', and copies of research data, mainly in the form of charts.