(1861-1938) Swiss physicist who studied measurement and alloy development.
He discovered a nickel-steel alloy, Invar, which showed negligible expansion with rising temperatures. He was awarded the Nobel Prize for Physics 1920.
As the son of a clockmaker, Guillaume came early in life to appreciate the value of precision in measurement. He spent most of his life at the International Bureau of Weights and Measures in Sčvres, France, which established the standards for the meter, liter, and kilogram.