framework of the Monographic Courses of High Studies of Exchange promoted by the Commonwealth of Catalonia. He also participated in the Minerva Collection, where he published "The radium". In 1919 set up the Institute of Electricity and Applied Mechanics and was its director; he was also a teacher of the section of electrotechnics of the Escola del Treball. He was interested in photography, a new practice in the early 20th century, using it to illustrate his technical and scientific works as well as his personal life. The theories of quanta and relativity captivated him, and he invited such figures as Jacques Hadamard) (1921), Hermann Weyl (1921), Arnold Sommerfeld (1922), Tullio Levi-Civita (1922) and Albert Einstein (1923) to Barcelona. Einstein's Spanish visit, between 22 and 28 February 1923, was a notable success, organized by Terradas, the Catalan Government, the Mancomunitat, and Rafael Campalans. Terradas was also the driving force behind a series of scientific monographs that were a compilation of these lectures, his own and the works of others (including Julio Palacios, Julio Rey Pastor and Jacques Hadamard), published by the Institute of Catalan Studies under the title "Physics and Mathematics Courses". He lectured at several universities in South America: in Buenos Aires and Rio de la Plata (Uruguay) from 1936 to 39. Terradas was the first professor to hold the chair in Differential Equation when it was first established in Madrid in 1932. Industries consultant On 1918, Terrades was chosen to drive the Xarxa de Ferrocarrils Secundaris de Catalunya (Secondary Net of Catalan Railways), intended to decentralize Catalonia, but was never completed due to the dictatorship of Primo de Rivera being established on 13 September 1923. He was a technical director of the Commonwealth of Catalonia railways, he directed (1923–25) and projected the construction of the Transversal Metropolitan Railway of Barcelona and other Catalan railway lines. It is said that the President of the Commonwealth of Catalonia, Josep Puig i Cadafalch, entrusted him a study about the stability of the turn of plain brick, known as the "Catalan turn", which is kept at the archive of the Institute of Catalan Studies. From 1940 onwards he worked for the Spanish Instituto Nacional de Industria, becoming one of the top consultants of the Spanish industrial development along the 40s. He specially was involved in the planning and design of the power plants built by Endesa by that time. He worked too at