In 1811 Brocchi produced a valuable essay entitled Memoria mineralogica sulla Valle di Fassa in Tirolo; but his most important work is the Conchiologia fossile subapennina con osservazioni geologiche sugli Apennini, e sul suolo adiacente (2 vols., Milan, 1814), containing accurate details of the structure of the Apennine range, and an account of the fossils of the Italian Tertiary strata compared with existing species. These subjects were further illustrated by his geognostic map, and his Catalogo ragionato di una raccolta di rocce, disposto con ordine geografico, per servire alla geognosia dell' Italia (Milan, 1817). His work Dello stato fisico del suolo di Roma (1820), with its accompanying map, is likewise noteworthy. In it he corrected the erroneous views of Scipione Breislak, who conceived that Rome occupies the site of a volcano, to which he ascribed the volcanic materials that cover the seven hills. Brocchi pointed out that these materials were derived either from Monte Albano, an extinct volcano, twelve miles from the city, or from the Monti Cimini, still farther to the north.