L E C T U R E S A T T H E U N I V E R S I T Y O F M A D R I D 8 8 9 The procedure is, in any case, arbitrary, because we have taken the Γ ’s to have basic physical meaning, and then we take the simple expression as a tensor to deduce the laws of gravitation and electromagnetism by variation. Nevertheless, we avoid Weyl’s weak point. Up to now, the calculations I have made with respect to gravitational and electromagnet- ic fields have given results already known. As to the structure of electrons, the calculations are so complicated that I have not been able to obtain anything definitive up to the present. In a thundering round of applause, Professor Einstein ends his third lecture and, with it, the series he gave at the university.