Physicist and Mathematician. Clausius was one of the founders of thermodynamics. His most important paper, on the mechanical theory of heat, published in 1850, first stated the basic ideas of the second law of thermodynamics. In 1865 he introduced the concept of entropy. Clausius graduated from the University of Berlin in 1844, and got his doctorate from the University of Halle in 1848. He then taught in Berlin, Zürich, Würzburg, and Bonn. In 1870 Clausius organized an ambulance corps in the Franco-Prussian War. He was wounded in battle, leaving him with a lasting disability. He was awarded the Iron Cross for his services. His wife, Adelheid Rimpham, died in childbirth in 1875, leaving him to raise their six children. He continued to teach, but had less time for research thereafter. Clausius crater on the Moon was named in his honor.