De radiis visus et lucis in vitris perspectivis et iride tractatus Marci Antonii De Dominis. Per Ioannem Bartolum in lucem editus. In quo inter alia ostenditur ratio instrumenti cuiusdam ad clare videndum, quae sunt valde remota excogitati

THE NEWLY-INVENTED TELESCOPE AND THE RAINBOW

4to (210x154 mm). [8], 78, [2] pp. Collation: a⁴ A-K⁴. Woodcut printer's device on title page and several woodcut diagrams in text. Errata on final leaf recto. Later stiff vellum. Restoration to the bottom margin of the title page, a few leaves very slightly browned, some pale staining, but a very good, wide-margined copy.

Very rare first edition, edited by De Dominis's friend Giovanni Bartoli and by him dedicated to the marquis Giovanni Battista del Monte Santa Maria, of this early work on the telescope and the operation of lenses, which also contains, in the second part, a full correct explanation of the phenomenon of the rainbow.

“In the preface, Bartolo says that the work is based on notes prepared by De Dominis for his lectures at Padua and Brescia twenty years before; but he adds that De Dominis himself had revised these notes and inserted an explanation of the newly-invented telescope […] Bartolo implies that De Dominis was acquainted very early with the principle of the telescope: ‘Non eram nescius eum in iuventute omnes publice professum fuisse partes Philosophiae, ac proinde etiam Mathematicis rebus splendorem maximum addidisse; sciscitari saepius placuit, quidnam de novo Instrumento illo sentiret, quod nuper ad inspicienda quae sunt remotissima a Nostrate Viro insigni Mathematico Galileo in lucem editum ferebatur, et Venetiis potissimum publicatum' [‘I was not unaware that in his youth he had publicly professed all the branches of philosophy, and consequently that he had added great splendor to mathematical studies; it often pleased him to inquire what he thought of that new instrument, which had lately been brought to light by our distinguished mathematician Galileo for the inspection of the remotest things, and especially published at Venice']. De Dominis also remarks: ‘Id enim quemadmodum maxima admiratione affecit, et afficit plurimos ita mihi certe, qui in perspectivis ante multos, sed per multos etiam annos delectationis causa mentem exercui, nulli prorsus fuit admirationi, sed cum primum illud vidi (erat autem valde imperfectum) effectum duorum vitrorum aperte cognovi' [‘As this truly caused great wonder, and affects most people, so certainly it did to me, who had exercised my mind in the art of perspective before many and indeed also for many years for my pleasure, it was not at all surprising to anyone, and indeed when I saw it for the first time (and it was very imperfect) I clearly understood the effect of the two glasses'], De radiis visus, pp. 37-38” (Ockenden, op. cit., p. 42, text and note 6).

As a matter of fact De Dominis and Galileo were both teaching mathematics and physics in Padua around the same time and, even though it can't be proved, it is highly probable that they knew each other personally or at least each other's works. De Dominis' De radiis and Galileo's Sidereus nuncius were both published at a year's distance by the same printer, Tommaso Baglioni. The imprimatur of the De radiis, dated 3 February 1610, is signed by Giovanni Battista Breatto, the same who a few weeks later (8 March) also signed the printing license of the Sidereus. The reason why the publication of the De radiis was delayed by over a year (Bartoli's dedication to Del Monte is dated 1 October 1611) is unknown, but the fact that in its imprimatur it is recorded as a book of 69 pages (“Registrato in libro à Carte 69”) rather than the published 78, seems to suggest that De Dominis felt the need to update and increase the text after the publication of the Sidereus nuncius.

“De radiis visus et lucis deals with lenses, telescopes, and the rainbow. Dominis knew how light was refracted in its passage from one medium to another, but he was not always consistent in his assertions. He held that it was possible that in some cases light could pass through the border of a medium without being refracted -for instance, into a thin layer of water. In general, his observations on refraction in lenses were correct. After the invention of the telescope Dominis added its theoretical explanation to his work. His explanation was not entirely satisfactory, however, because his knowledge of the law of refraction was incomplete. He concluded that the image of an object was enlarged by increasing the angle of sight, which he had previously defined correctly. Thus Dominis describes in particular detail the effect on the angle of sight of a lens of greater curvature or of a greater distance between the lens and the object being viewed. With the same thoroughness he examined lens combinations, in particular the combination of a convex object glass and a concave eyepiece. This work led to his discovery of the conditions under which the magnification of an image is possible” (C.C. Gillispie, Dictionary of Scientific Biography, New York, 1971, IV, p. 158).

“Chapters 8-9 are on the telescope. It is here that De Dominis makes his famous claim regarding the telescope: ‘I am the first to break the ice' [‘Ut enim potui primus hoc gelu perfregi alijs viam muniens', p. 43]” (DiLaura, op. cit., p. 62).

The second part of the book deals with the explanation of the rainbow. De Dominis believed that the rainbow is caused by the refraction and the reflection of the light in raindrops. Even though the correct elementary theory of the rainbow had already been explained by the Persian physician Qutb Al-Din al-Shirazi (1236-1311) and the Dominican theologian Theodoric of Freiburg (Dietrich von Freiburg or Theodericus de Vriberch, ca. 1240-ca. 1320) as early as the beginning of the 14^th century, their work remained basically unknown for five centuries, despite Theodoric's explanation is presented by J. Trutfetter (1460-1519) in his Summa in tota physicen printed at Erfurt in 1514. Thus De Dominis is usually believed to have discovered the same results independently and to have published and made them available to the scientific community for the first time in the De radiis. So believed Isaac Newton, who refers to it twice in his Opticks (1704), acknowledging De Dominis as the first to offer a correct theory of the rainbow preceding Descartes, whose supporters on the contrary believed the first correct explanation of the rainbow was given in the latter's Discours (1637). Newton went even further by accusing Descartes of plagiarism, so closely his theory of the rainbow resembled that of De Dominis.

Marco Antonio de Dominis was born in 1566 on the Dalmatian island of Arbe (Rab in Croatian). He entered the Jesuit order at an early age, receiving his education in the Jesuit colleges of Novellara, Verona, Padua and Brescia, where he was ordained a priest in 1592 and completed his theological studies. Already during his noviciate he was appointed lecturer of mathematics at Padua, and of logic and rhetoric at Brescia. He then left the order in 1597 and was elected bishop of Segna (Senj in Croatian) in 1600 and archbishop of Spalato (Split in Croatian) in 1602. During the Venice interdict in 1606, De Dominis sided with Paolo Sarpi and fell into the Protestant orbit of the British ambassador in Venice, Dudley Carleton. In 1616, knowing that his rivals were collecting various written testimonies about compromising statements he had made against the Church, he decided to flee. He travelled through the Grisons and Basel, making a stop in Heidelberg, where he published the booklet Causae profectionis suae ex Italia, a sort of short biography where he explains the reasons of his escape. He then arrived in London, where James I made him dean of Windsor. In the meantime in Rome all his writings, mostly left unpublished, were condemned by the Inquisition as “heretical, erroneous and schismatic”. In the following years he published several works at the presses of the royal typographer John Bill, including in 1619 Paolo Sarpi's history of the Council of Trent, that he dedicated to the king. However over the course of the following year, De Dominis' relations with his English protectors gradually deteriorated. He thus appealed to Pope Gregory XV, an old friend and schoolmate of his, promising a renunciation of his Protestantism if he could return to Rome. In 1622 he formally abjured and condemned Sarpi's book. After the death of Gregory XV in 1623, however, De Dominis lost his protector and under the new Pope Urban VIII was soon denounced and arrested. He died while detained in the papal prison at Castel Sant'Angelo. His book on tides, Euripus seu de fluxu et refluxu maris, appeared posthumously at Rome in 1624. Three months after his death, De Dominis' soul was formally condemned, his properties confiscated, and his exhumed body publicly burned along with all his books. All his works were eventually placed on the Index librorum prohibitorum. This fact may explain the rarity of all his writings including the De radiis (cf. S. Cavazza, De Dominis, Marcantonio, in: “Dizionario Biografico degli Italiani”, vol. 33, 1987, s.v.).

A. Carli & A. Favaro, Bibliografia galileiana, Rome, 1896, no. 37; D. Cinti, Biblioteca galileiana, Florence, 1957, no. 33; P. Riccardi, Biblioteca matematica italiana, Milan, 1952, I, cols. 447-448; R.E. Ockenden, Marco Antonio de Dominis and His Explanation of the Rainbow, in: “Isis”, 26, no. 1, 1936, pp. 40-49; A. Ziggelaar, Die Erklärung des Regenbogens durch Marcantonio de Dominis, 1611, in: “Centaurus”, 23, no. 1, 1979, pp. 21-50; D.L. DiLaura, Biblioteca Opticoria, Boulder (CO), 2021, no. 55.

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