Besides the numerous commentaries in Vols. IX, X, XI, XII, and XIII of the October "Acta Sanctorum", which won much praise, Father de Buck published in Latin, French and Dutch a large number of little works of piety and dissertations on devotion to the saints, church history, and Christian archaeology. The partial enumeration of these works fills two folio columns of his eulogy, in the forepart of vol. II of the November "Acta". Because of his extensive learning and investigating turn of mind he was naturally bent upon probing abstruse and perplexing questions. Thus in 1862 he was led to publish in the form of a letter to his brother Remi, then professor of church history at the theological college of Louvain and soon afterwards his colleague on the Bollandist work, a Latin dissertation, "De solemnitate praecipue paupertatis religiosae". This was followed in 1863 and 1864 by two treatises in French, one under the title "Solution amiable de la question des couvents" and the other "De l'état religieux", treating of the religious life in Belgium in the nineteenth century.