DE ROSSI, MICHELE STEFANO. — Geologist, born in Rome on 30 October 1834 and died at Rocca di Papa on 23 October 1898, he was the inseparable companion in the Giovanni Battista (v.) for whom he drew plans and sections, including of the most hidden and dangerous parts of the Roman catacombs.
Highly versed in the natural sciences and particularly in geology, he applied this knowledge to the study of the cemeteries, thus offering, in his appendices to the three volumes of his brother’s Roma sotterranea, a truly positive contribution with his Analisi geologica ed architettonica del cimitero di Callisto (Rome 1867). With this work he put the seal on the demonstration by Fr. G. MARCIA (v.) of the wholly Christian origin of the catacombs, making known their extent, studying the laws and limits of the excavations, and in particular establishing, with technical arguments, the chronology of part of the cemetery of Callistus. Among his articles in this field are the two published in Rome in the Atti dell’Accademia dei nuovi Lincei: Dell'ampiezza delle romane catacombe e d'una macchina iconografica ed ortografica per rilevarne le piante ed i livelli (1860) and Quale metodo tecnico adoperarono i fossori per dirigere l'escavazione nel labirinto dei cimiteri suburbani di Roma, 33 (1880), pp. 418–26.
Numerous important studies on terrestrial dynamism are due to him; in order to observe it, he invented ingenious instruments. Thanks to his efforts, the Italian government established a geodynamic observatory at Rocca di Papa, of which he was appointed director. He presented his principal seismological investigations in La meteorologia endogena (2 vols., Milan 1879–82). He also made important observations in the Bollettino del vulcanismo italiano, which he founded and directed from 1874 to 1897. His writings in the field of palaethnology are also numerous.