He devoted himself to the study of the Church Fathers, also to Pagan and Christian antiquities; he and Giovanni Battista de Rossi became the principal disciples of Giuseppe Marchi.
In 1872 he began the publication of a monumental history of early Christian antiquities, entitled Storia dell'arte cristiana.
It was destined to include all works of sculpture, painting, and the minor and industrial arts, during the first eight centuries of the Christian Era.
It is a general history of early Christian art, and contains five hundred finely engraved plates and explanatory text.
Among them are the aforementioned Storia dell'arte cristiana nei primi otto secoli della chiesa (6 vols.