(b. Rome, Italy, 17 August 1750; d. Milan, Italy, 15 February 1826)
geology, natural history.
Breislak, of German extraction, was a priest who devoted much of his life to the teaching of the natural sciences. He had become interested in them during his early youth, which he spent in Sicily; and when he returned to Rome, he improved his scientific knowledge under Giovanni Fortis and Pietro Petrini. He later published reports on the natural resources of Latium: the Tolfa, Allumiere, Oriolo Romano, Latera, and Civitavecchia mines; underground water; and agriculture.
Subsequently, Breislak moved to Naples, where he taught at the military academy. In 1794 he witnessed the eruption of Vesuvius and made direct observations at the Campi Flegrei and Pozzuoli sulfur mines. Topografia fisica della Campania (1798), which discusses his studies on volcanoes, includes his opinion that thevolcanic systems of Latium and Campania were connected at the ancient Roccamonfina volcano, whose eruptive apparatus and lava he had discovered. An adherent of Plutonist theory, Breislak believed that metamorphic rocks originated during consolidation of the earth’s crust.
Considered one of the founders of volcanology in Italy, Breislak was the first to determine that basaltic rocks were of extrusive origin; he also emphasized that the tufaceous deposits of Campania originated under water, and he reconstructed the evolution of Vesuvius. He concluded that for a long time Monte Somma, the second summit of Vesuvius, had been the sole volcanic apparatus; that it had been active until a.d. 79; that it had been eroded; and that the cone of Vesuvius had been set upon it within historical time.
Breislak’s final move was to Milan, where he was inspector of the niter factory and cooperated with the Biblioteca Italiana. He also investigated the mineral resources of most of Lombarby, particularly the building-stone and clay quarries of Brianza and the gold placers of the Tessin, Adda, and Serio rivers. In addition, he studied the igneous rocks on the western shore of Lake Maggiore, between Intra (Verbania) and Arona.
Breislak’s writings are Topografia fisica dells Campania (1798); Voyages Physiques et lithologiques dans la Campanie, suivis d’une mémoire sur la constitution physique de Rome (1801), also trans. into German (Leipzig, 1802); Descrizione geologica della provincia di Milano (1822); and Traité sur la structure interne du globe (1822).