Ii.; Jules Brunfaut, De l'Exploitation des soufres (2nd ed., 1874); Georgio Spezia, Sull' origine del solfo nei giacementi solfiferi della Sicilia (Turin, 1892).
On his own initiative he conducted exhaustive inquiries into the conditions of the Sicilian peasants and of the Tuscan metayers, and in 1877 published in co-operation with Signor Leopoldo Franchetti a masterly work on Sicily (La Sicilia, Florence, 1877).
Fahrer, Forschungen zur Sicilia sotterranea (Munich, 1897); and D.
The bishopric of Malta is referred to by Rocco Pirro (Sicilia sacra), and by Gregory the Great (Epist.