The Danish-born mathematician Olaus Henrici studied engineering and them mathematics in Germany, settling in England in 1865. Henrici first worked as an engineer but then taught at University College London and, from 1884, at the Central Institution in South Kensington. At both schools, he arranged space for the construction of mathematical models. In 1873, his interlocking paper model of a second order surface was exhibited at a meeting of mathematicians in Göttingen. Alexander Brill of what would become the technical university in Munich, attended the meeting and was much impressed. Brill designed a series of such paper models, all made up of circular discs and arcs of discs. Alexander Brill apparently first simply displayed these, but by 1888, his brother, the publisher Ludwig Brill, was selling them as “Carton Models.” This was the first of numerous series of mathematical models that L. Brill and his successor Martin Schilling would publish over the next decades. The Smithsonian has two examples of this series, one exhibited at the 1893 world’s fair in Chicago and sold by Brill to Wesleyan University and the second sold by Schilling to the mathematics department at Brown University.
