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Magiotti, Raffaello


(b. Montevarchi, Italy, 1597; d. Rome, Italy, 1656)

physics, hydrostatics, hydrodynamics.

Raffaello Magiotti studied in Florence and was one of the three favored pupils, along with Castelli and Torricelli, whom Galileo referred to as his Roman “triumvirate.” After becoming a priest in the order of Santa Lucia della Chiavica, he was invited to accompany Cardinal Sacchetti to Rome around 1630 as his houseguest. At Rome Magiotti became well known as a scholar in mathematics, law, medicine, theology, and letters. His wide culture secured for him an appointment as scrittore in May 1636 on the scholarly staff of the Vatican Library with a salary of 200 scudi a year. Although Galileo, with whom he maintained a lively correspondence, and Castelli wished to nominate him (1638–1640) for the chair of mathematics at Pisa, Magiotti refused to leave the congenial intellectual life of Rome, where he died in 1656 of the plague.

It was probably Magiotti who, stimulated by Galileo’s treatment of siphons in the Two New Sciences (1638), encouraged acquaintances at Rome to experiment further on siphons and the vacuum. At any rate, Magiotti was present at an experiment that was devised and staged at Rome by Berti, probably in 1640, but definitely at some time between December 1638 and 2 January 1644. From the description thereof left by Magiotti and other eyewitnesses, this experiment resembled the later “barometric” experiment performed by Torricelli in 1643–1644, although it is not clear whether Berti was trying to demonstrate air pressure. In a letter addressed to Marin Mersenne some years later (12 March 1648) Magiotti says that he had earlier forwarded news of the Berti experiment to Torricelli and had suggested that the use of a liquid such as seawater, which would be heavier than the plain water used by Berti, would make a significant difference in the result. “They [Torricelli and Viviani] then carried out experiments and eventually arrived at [the use of] mercury.”

In the field of hydrodynamics, Torricelli openly acknowledged the aid of Magiotti. According to Torricelli’s theory of flow (1643), the mean velocities of a liquid flowing out of the bottom outlet of a vessel are proportional to the square root of the head pressure, that is, the column of liquid above the outlet. This hypothesis was borne out experimentally by Magiotti who then determined the rate of flow through various sizes of openings. Magiotti thus anticipated by nearly thirty years the similar experiments of Edme Mariotte (1673). (Not surprisingly Torricelli greatly admired Magiotti and sought the priest’s approval of his work on solid cycloids.)

Only one work by Magiotti was printed during his lifetime, the Renitenza dell’ Acqua alla Compressione (1648). This work, in the form of a letter to Lorenzo de’ Medici, embodies the first published announcement of the near incompressibility of water at a constant temperature—although Magiotti errs by insisting that water is absolutely incompressible—-and the expansion and contraction of water and air according to changes in temperature. Several thermometers and other devices are mentioned, the most interesting being a “Cartesian devil” or “diver.” In Magiotti’s description, a stoppered cylinder containing an empty inverted jug is filled with water. As the stopper at the top is pushed into or withdrawn from the cylinder, the varying compression makes the jug fall or rise. The effect is caused by the incompressibility of the water. When the stopper is pushed into the cylinder, touching the water directly with no air space in between, the water forces itself into the jug, compressing the air therein and forcing the jug to descend. When the pressure is relaxed, the decompressed air forces the water out of jug, which, again being lighter than water, rises to the surface. Although a related effect had been described earlier by Beeckman, Magiotti’s is the first thorough—and the first printed—description of the Cartesian devil.

After Magiotti died, Leopold de’s Medici commissioned Borelli in 1658 to seek out the late priest’s manuscripts in Rome. Borelli reported that the writings had been destroyed by looters two years before. Despite this loss, however, Magiotti holds an important place in the history of science because of his probable connection with the first experiment to produce the vacuum, his experiments on hydrodynamics, and his announcement of the incompressibility of water.


1. Original Works. Magiotti’s Renitenza certissima dell’ acqua alla compressione (Rome, 1648) was reprinted in G. Targioni-Tozzetti, Atti e memorie inedite dell’ Accademia del Cimento e Notizie aneddote dei progressi delle scienze in Toscana, II (Florence, 1780), 182–191; and in L. Belloni, “Schemi e modelli della macchina vivente nel Seicento, con ristampa della lettera di R. Magiotti. …,” in Physis, 5 (1963), 259–298. A MS version of the work is among the Galilean MSS at the Biblioteca Nazionale Centrale in Florence. The autograph of Magiotti’s letter to Mersenne on the Berti vacuum experiment is in the Nationalbibliothek, Vienna, MS 7049, no. 127; it was printed in C. De Waard, L’expérience barométrique; ses antécédents et ses explications (Thouars, 1936), 178–181. The correspondence with Galileo is in A. Favaro, ed., Opere di Galileo Galilei XVIII (Florence, 1890–), 525. Correspondence with Torricelli is in G. Loria and G. Loria, eds., Opere di Evangelista Torricelli, III (Faenza, 1919), 75 (cf. 37, 43, 102, 109, 150, 165, 204). A letter to Candido del Buono on the comet of December 1652 appears in A. Fabroni, ed., Lettere inedite di uomini illustri, II (Florence, 1775), 259–263 (cf. I, 151–152).

II. Secondary Literature. A life of Magiotti is in G. Targioni-Tozzetti, op. cit., I, 171–172. Also see Opere di Galileo, XX, 472–473. For Magiotti’s role in the vacuum experiment and his other work see De waard, op. cit., 101–117, 132–137; W. E. K. Middleton, The History of the Barometer (Baltimore, 1964), 10–18; and Invention of the Meteorological Instruments (Baltimore, 1969), 3–18. For Torricelli’s opionion of Magiotti, see Opere di Galileo, XVIII, 327, 331–332; and Opere di Evangelista Torricelli, I, 174, which also cites Magiotti’ experimental verification of the theory of flow, II, 190.

Descriptions of the Berti experiment by Zucchi, Kircher, Maignan and K. Schott are reprinted by De Waard, op.cit., 145 ff.

For the Cartesian devil, see G. Govi, “In che tempo e da chi siano inventati i ludioni, detti ordinariamente ‘Diavoletti Cartesiani,’” in Rendiconti dell’ Accademia delle scienze fisiche e matematiche, 18 (1879), 291–296.

Paul Lawrence Rose

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