Soon after his return, the pope (Pius VI.) gave him a dispensation from his monastic engagements, and he lived subsequently as a secular priest. In 1778 he made a journey to Switzerland, where he con ceived the idea of writing a tract on subterranean rivers ; and this, with dissertations on the meteorological influence of the moon, on conductors of electricity, and on the heat of the earth, he published at Milan, In 1781, under the title of Opuscoli Filosofici.' In the year 1776, having previously enjoyed excellent health, he first felt the symptoms of a painful disease ; these gradually increased in violence, and eight years afterwards, in the hope of obtaining relief, he underwent an operation : a mortification however ensued, and terminated his life at Milan, November 22, 1784, in his sixty-seventh year. He was buried in the church of St. Alexander in that city, and the Barnabites honoured his tomb with an epitaph in Latin.
In 1757 Frisi was elected a Fellow of the Royal Society of London : he was also a member of the Academy of Sciences of St. Petersburg, of the Academies of Berlin, Stockholm, Copenhagen, and Berne, and of the Institute of Bologna. He received a golden medal in 1759 from the archduke Joseph, afterwards emperor ; and the empress Maria Theresa granted him a pension for life.
Besides the works which have been mentioned Frisi published many others ; and of these the following aro the principal :—'Pre lectio habits Mediolani,' viii. idus Maii, (1764;) Saggio sopra l'Archi
tettura Gotica ' (Leghorn, 1766); De Gravitate Universali libri tree ' (Milan, 1768), a work much praised by D'Alembert and John Bernoulli ; 'Della Maniere di preservare gli Edifizi dal Fulmine ' (Milan, 1768); 'Danielle Melandri et Pauli Frisii alterius ad alterum de Theoria LULID3 Commentarii ' (Parma, 1769); ' Cosmogmphiaa Physical et Mathe maticte,' 2 tom. 4to. (Milan,. 1774, 1775)—this is considered his prin cipal work ; 'Del' Architettura, Statica, e Idraulica' (Milan, 1777) Pauli Frisii Operum :' tom. 1, Algebram et Geometriam Aualyticarn continens (Milan, 1782) ; tom. 2, Mechanicam Univei-sam et Meehaaiere Applicationem ad Aquarum Fluentium Theoriam (ibit], 1783). The third volume, which treats of Cosmography, was published by two of his brothers after his death. Ho published, at various times, notices of the lives of Galileo Galilei and Bonaventura Cavalieri, of Sir Isaac Newton, Donato Silva, and Titus Pomponius Atticus : he wrote a notice of the empress Maria Theresa, which was published at Pisa in 1783, without his name ; and one of D'Alembert, which was published after his death. He also left several works in manuscript.