Carl Friedrich Gaus, German mathematician, mid 19th century.
© Science Museum / Science & Society Picture Library
Photogravure after a painting by Jensen. Carl Friedrich Gaus (1777-1855) together with Baron Augustin Louis Cauchy, founded the modern form of complex analysis, which was to have a profound effect on mathematics for the rest of the 19th century. He was also the inventor of the heliotrope, a surveying instrument.