Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
Charles-Edouard Guillaume (1861-1936) was a Swiss scientist who worked at the International Bureau of Weights and Measures for over fifty years, where he was responsible for calibration of thermometers and studies of thermal expansion of the standards of length, such as the International Meter. His discovery of a steel-nickel alloy called invar that was impervious to temperature changes advanced the development of precision instruments significantly. For this discovery and its many applications he received the 1920 Nobel prize in physics.