ANTONELLI, GIOVANNI. - Scholastic scientist of the Piarists, born in Candeglia, a suburb of Pistoia, on 10 January 1818, died in Florence on 14 January 1871. Having become a Piarist on 7 November 1834, he was a pupil of Fr. Giovanni Inghirami, succeeding him in the chair of higher mathematics and astronomy and in the directorship of the Ximenian Observatory in Florence. In his scientific teaching, the author continued the fine Piarist traditions, distinguishing himself with his particular astronomical and meteorological observations. His ingenious idea of deriving assistance from the optical state of the atmosphere to investigate meteorological conditions is still judged (to this day) as highly original.
In 1855 he published a work of great mathematical value on the concept of the infinite and of infinitesimals as applied to differential calculus: *Di un nuovo modo di trattare il calcolo differenziale col principio infinitesimale*. The following year he communicated an original essay on geometrical ideology to the Accademia dei Georgofili.
With a Galilean spirit, he sought to put his theoretical principles into practice, applying them, in their abundant variety, to problems of advanced mathematics, physics, and mechanics. Notable among his studies are those for the improvement of the celebrated invention of the internal combustion engine, due to his confrere Eugenio Barsanti, and of another ingenious machine for better utilizing the force of steam, devised by himself in collaboration with Fr. Cecchi.
As an astronomer, he diligently restored in Santa Maria del Fiore the famous gnomon of Paolo Toscanelli; he observed the satellite of Sirius with the Clerck telescope and devoted himself to interpreting the scientific problems of the *Divine Comedy*, compiling the classic notes inserted by Tommaseo in his commentary on the poem.
The versatile genius of the author also distinguished itself in solving hydraulic problems for the reclamation of the Fucecchio marsh and for the regulation of Lake Orbetello. A special characteristic of Antonelli’s scientific activity is his application of his studies in mathematics and geodesy to the drafting of projects for new railways. Essentially his own are the projects for the lines from Florence to Lake Trasimeno via Arezzo and from Florence to Faenza.
BIBL. N. Tommaseo, *Commentazione di G. A.*, Florence 1872 (2nd ed. with variants and additions inserted by the author, Florence 1939, edited by Fr. V. Viti); A. Stiatteis, *Intorno alla vita e agli scritti del p. G. A.*, in *Boll. di Bibliografia e di Storia delle scienze matematiche e fisiche*, Rome 1873; G. Giovannozzi, *Il p. G. A.*, Pistoia 1910.