ANTONELLI, GIOVANNI. - Piarist scientist, b. at Candeglia, a suburb of Pistoia, on 10 January 1818, d. at Florence on 14 January 1871. Having become a Piarist on 7 November 1834, he was a disciple of Fr. Giovanni Inghirami, whom he succeeded in the chair of higher mathematics and astronomy and in the directorship of the Ximenian Observatory in Florence. In his scientific teaching, A. continued the fine Piarist traditions, distinguishing himself by his particular astronomical and meteorological observations. His idea of drawing assistance from the optical state of the atmosphere in order to investigate its meteorological state is judged (to this day) to be most ingenious. In 1855 he published a work of great mathematical value on the concept of the infinite and of infinitesimals applied to differential calculus: Di un nuovo modo di trattare il calcolo differenziale col principio infinitesimale. The following year he communicated to the Accademia dei Georgofili an original essay in geometric ideology.
With a Galilean spirit, he sought to put his theoretical principles into practice, applying them, in their copious variety, to problems of advanced mathematics, physics and mechanics. Noteworthy are his studies for the improvement of the celebrated invention of the internal combustion engine, due to his fellow citizen Eugenio Barsanti, and of the other ingenious machine for making better use of steam power, devised by himself in collaboration with Fr. Cecchi.
As an astronomer, he carried out the diligent restoration in S. Maria del Fiore of the famous gnomon of Paolo Toscanelli; he anticipated Clark in the observation of the satellite of Sirius and devoted himself to the interpretation of the scientific problems of the Divine Comedy, compiling the classic notes inserted by Tommaso in his commentary on the poem.
The many-sided genius of A. also distinguished itself in the solution of hydraulic problems for the reclamation of the Fucecchio marsh and for the regulation of the lake of Orbetello. A special characteristic of Antonelli's scientific activity is that of having applied his studies of mathematics and geodesy to the drafting of projects for new railways. Substantially his are the projects for the lines from Florence to Lake Trasimeno via Arezzo and from Florence to Faenza.