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