As editor of the journal *Maria Immacolata*, he conceived the idea of fostering a scientific missionary movement. Besides some historical essays, in articles such as *Die theologisch-wissenschaftliche Missionskunde* (1909) and *Die Mission in Exegese und Patrologie* (1909), he published his first attempts at a scientific treatment of missionary matters. At the Congress of German Catholics in Breslau (1909), a permanent missionary commission was appointed. At its first meeting in Berlin in 1910, Fr. S. delivered a report on *The Duties and Tasks of Science in Relation to Missions* and, commissioned by the same body, drafted memoranda on the state of historiography, the need for a universal missionary bibliography—already envisaged by him—and for a scientific missionary journal. Meanwhile, Prof. Schmidlin, under Fr. S.’s impetus, entered the movement and realized the scientific missionary journal, the creation of a university chair for missionary science, and the academic missionary movement among students. Fr. S., however, concentrated all his energies on the publication of an extensive missionary bibliography. In 1916 the first volume of the general *Bibliotheca missionum* appeared. In 1924 the second volume followed, covering the early centuries of American literature. Meanwhile he was called to Rome. The work on the *Bibliotheca missionum*, greatly facilitated by the literary material gathered for the 1925 Exhibition and in other Roman libraries, proceeded at an accelerated pace. In 1927 the third volume was completed, concluding the American literature; in 1928 and 1929 the fourth and fifth volumes appeared, the first dealing with the vast Asian literature. These three volumes were published in collaboration with Fr. Giovanni Dindinger, O.M.I. After Fr. S.’s death in 1930, the work was continued by Fr. Giovanni Rommerskirchen, O.M.I., with the assistance of Fr. Dindinger, and assumed ever greater proportions. By 1951 eight further volumes had been published. Pius XI entrusted Fr. S. with making accessible to the world the statistical material on missions collected for the Vatican Missionary Exhibition, in the form of diagrams with explanatory texts, *Die Weltmission der katholischen Kirche, Zahlen und Zeichen*, which appeared in 1927–28 in five languages.
Fr. S. may be called one of the principal elders and pioneers of Catholic missionary science.