 Korteweg (1848–1941) was professor of mathematics, mechanics and astronomy at the University of Amsterdam from 1881–1918; the last five years as extraordinarius, so as to make place for Brouwer. Around 1900, Korteweg was the most important and influential mathematician in the Netherlands, and he contributed much to the internationalisation of Dutch mathematics. A mathematical physicist trained by van der Waals, he had a particular interest in mechanics and thermodynamics. Among his many results, the best-known is probably the Korteweg-de Vries equation, describing the behaviour of waves in a shallow channel. Korteweg also had a strong historical interest, and was chief editor of vols. XI–XV of Christiaan Huygens’ collected works (1908–1925). Part of the correspondence with his PhD student Brouwer concerned the unification of physical theories (see van Stigt, 1990, pp. 490–498). 