Orazio Grassi

Orazio Grassi SJ (b. Savona 1 May 1583 – d. Rome 23 July 1654) was an Italian Jesuit priest, who is best noted as a mathematician, astronomer and architect.

[2] Early in 1619, under the title "De Tribus Cometis Anni MDCXVIII", Grassi published a lecture he had given to the Collegio Romano about three comets which had appeared in the autumn of 1618.

[6] Grassi replied in turn with his treatise Libra astronomica ac philosophica published under the pseudonym of Lotario Sarsi Sigensano (an anagram of Horatius Grassius Salonensis, his name in Latin).

In this Grassi both noted how close the ideas in Galileo's Discourse were to those advanced by Gerolamo Cardano and Bernardino Telesio (which the Church regarded as dangerous) and set out scientific arguments and experimental test results to show that comets were definitely not optical illusions.

[7] Although most scholars do not agree that Grassi was its author,[8] it is noteworthy that his second response to Il Saggiatore, the Ratio ponderum librae et simbellae (1626), contains many of the same arguments as the anonymous complaint.

In the later period of his life, when he was in Genoa, he produced a number of other works, subsequently lost, including one treatise on the physics of light and another on architecture, unfinished at the time of his death.

There he served not in a teaching capacity but as confessor, but although he no longer held a senior academic post, he continued to review and advise on a number of the Order's scientific projects.

His interest in architecture appears to date from 1616 when he began teaching mathematics, and at the same time assumed the title consiliarius aedificiorum (building consultant), for all the construction projects of the Jesuit order.

It was his only completely realised design, and it was a major influence on Jesuit architecture, combining excellent functional use of space with sober decoration.

[2] In the Spring of 1645 Grassi visited Rome, where he carried out an inspection of the works on Sant'Ignazio and wrote a highly critical report, resulting in a general review of the construction that had already been completed under the direction of Antonio Sasso.

Grassi was responsible for work relating to the elevation of the facade, and proposed a novel interior dome scheme to solve other problems arising from earlier departures from the original design.