Stock Photo - Dec. 12, 1964 - Julius Robert Mayer-Commemorative exhibition. On the occasion of the 150th anniversary of Robert Julius Mayer's birthday in the Munich 'German Museum' from December 4th, till March 1965 a commemorative exhibition takes place. Documents, pictures and printed products, gathered by libraries private collection, are giving a view over the life and work of the famous naturalist who discovered one of the most important physical law, the production of energy and the mechanical thermal equivalent. OPS: A dynamometer, discovered by Julius Robert Mayer in the years 1868/69. With this instrument the discoverer demonstreated, that it is possible to produce energy heat and heating. (Credit Image: © Keystone Press Agency/Keystone USA via ZUMAPRESS.com)