Anton Gaudí preserved this drawing of a sloping declining solar clock, signed on May 3, 1873. It was an exercise of gnomic for the subject "Estereotomía de la piedra, la madera y el hierro y aplicaciones de la geometría descriptiva y gnomónica", that was giving Antoni Rovira i Rabassa. At the time, the Spanish Republic had just been proclaimed and Anton was twenty years old. Still he was preparing the entrance examinations in the School of Architecture, but already he had registered of four subjects. That year, he was living in Barcelona with his brother Francesc, in house of their mother single aunt Úrsula Cornet. We do not know what it happened in the ordinary summons of June, 1873. The civil war was very virulent in Catalonia and the Carlists entered Riudoms on July 25, 1873. Gaudí requested to examine in the summons of October, 1873, but we do not know what he did, and neither do we know what happened in that of June, 1874. In the summons of October 21, 1874, the same one in which he overcame the entrance examinations in the School of Architecture, Gaudí there appeared to Stereotomy, in front the tribunal formed by Leandre Serrallach, Antoni Rovira and Josep Vilaseca, which suspended him. And, finally, in the following summons, on June 30, 1875 - six months after the Restoration of the new king Alfonso XII-, he approved the Stereotomy by the tribunal formed by Joan Torras, Antoni Rovira and August Font.