Jacquier, François

JACQUIER, FRANÇOIS. - Philosopher, mathematician, astronomer of the Order of Minims, b. at Vitry-les-Français on 7 June 1711, d. at Rome on 3 July 1788.

Sent to Rome, he completed his studies at the Convent of the Trinità dei Monti, and in Rome, in collaboration with his confrere Le Seur (v.), he carried on his scientific activity. He taught philosophy, theology, but particularly mathematics at the Trinità de' Monti, at the Sapienza, and at Propaganda Fide. The opinion of the two scientists was often sought by the supreme pontiffs and by scholars on the most important problems of architecture, statics, hydraulics, etc. In 1746 their project, in collaboration with Fr. R. Boscovich (v.), for the stability of the Vatican dome, was preferred and carried out by encircling the Michelangelesque structure with five iron bands. Both were members of the principal academies of Europe. J. (after the suppression of the Jesuits) held the chair of mathematics at the Collegio Romano. He also occupied himself with music and with aerostatics (cf. G. Boffito, Una memoria aeronautica del p. J. [1783], in Rivista aeronautica, 8 [1932], pp. 669-77 and 219-20).

Besides the various answers to questions put to him, and a commentary on Newton's mathematical principles, in collaboration with Fr. Le Seur, he wrote: Del calcolo integrale (Parma 1768); Institutiones philosophicae ad studia theologica accomodatae (4 vols., Rome 1749, many editions and versions in Italy and abroad); Trattato intorno alla sfera (Parma 1775); Descrizione di uno strumento per fare orologi solari (ibid. 1774).