JACQUIER, FRANÇOIS. — Philosopher, mathematician, and astronomer of the Order of Minims, born at Vitry-les-Français on 7 June 1711, died at Rome on 3 July 1788.
Sent to Rome, he completed his studies at the Convent of Trinità dei Monti, and in Rome, in collaboration with confrère Le Seur (v.), carried out his scientific work. He taught philosophy, theology, but especially mathematics, at Trinità de’ Monti, the Sapienza, and Propaganda Fide. The opinions of the two scientists were often sought by the supreme pontiffs and by scholars on the most important problems of architecture, statics, hydraulics, etc. In 1746 their project, prepared in collaboration with Fr. R. BOLSCEVISMO (v.), for the stability of the Vatican dome was preferred and implemented by encircling Michelangelo’s structure with five iron bands. Both were members of the principal academies of Europe. J. (after the suppression of the Jesuits) obtained the chair of mathematics at the Roman College. He also concerned himself with music and aerostatics (cf. G. Boffito, Una memoria aeronautica del p. J. [1783], in Rivista aeronautica, 8 [1932], pp. 669–77 and 219–20).
In addition to the various answers to the questions addressed to him, and to a commentary on Newton’s mathematical principles, he wrote, in collaboration with Fr. Le Seur: 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).