Istoria e Dimostrazioni Intorno alle Macchie Solari e Loro Accidenti ... Si aggiungono nel fine le Lettere, e Disquisizioni del finto Apelle. Rome: Giacomo Mascardi, 1613.

FIRST EDITION OF GALILEO'S FIRST PUBLISHED ENDORSEMENT OF THE COPERNICAN MODEL, his “Letters on Sunspots.” This preferred “domestic” issue, quarto, two parts in one volume, includes Scheiner’s letters (to which Galileo was responding), a portrait of Galileo, thirty-eight full-page engravings of sunspots, five full-page engravings of Jupiter’s satellite plates (two neatly remargined along fore-edge).

In this work, Galileo's publishes his endorsement of the Copernican system of the universe for the first time. Galileo wrote the Istoria e dimostrazione in the form of letters to Marcus Welser of Augsburg, arguing that sunspots appeared on (or near) the surface of the sun and were not tiny satellites of it. The work also includes Galileo's first written account of his observations of the phases of Venus and the mysteries of Saturn. Careful observations of sun spots allowed Galileo to conclude that the sun rotated on a fixed axis. His specific endorsement of the Copernican model foreshadowed many of his later theories and their political and religious consequences: "I tell you that this planet also, perhaps no less than horned Venus, agrees admirably with the great Copernican system on which propitious winds now universally are seen to blow..."

“After a brief controversy about floating bodies, Galileo again turned his attention to the heavens and entered a debate with Christoph Scheiner (1573–1650), a German Jesuit and professor of mathematics at Ingolstadt, about the nature of sunspots (of which Galileo was an independent discoverer). This controversy resulted in Galileo’s Istoria e dimostrazioni intorno alle macchie solari e loro accidenti (“History and Demonstrations Concerning Sunspots and Their Properties,” or “Letters on Sunspots”), which appeared in 1613. Against Scheiner, who, in an effort to save the perfection of the Sun, argued that sunspots are satellites of the Sun, Galileo argued that the spots are on or near the Sun’s surface, and he bolstered his argument with a series of detailed engravings of his observations” (Britannica).

Galileo's account of sunspots "was a momentous discovery at the time since, as we have seen, the Aristotelians maintained that nothing could change in the heavens, and surely not the eternal and immutable Sun! Galileo's discovery that devastating change occurred on the very face of the Sun was yet another blow to the traditional world view" (The Cambridge Companion to Galileo).

Two different issues of Galileo’s Istoria e Dimostrazioni intorno alle Macchie Solari are known, published at the same time. This "domestic" issue, with separate half-title and paging, contains the second part, "De maculis solaribus tres epistolae,", letters written to Welser by the Jesuit Christoph Scheiner. This correspondence, in which Scheiner promotes his theory that sunspots are small planets, prompted Galileo to publish his account of his own observations. This issue and another, lacking Scheiner's letters, known as the “export issue,” have no known priority. This issue, known as "domestic" is one evidently for the Italian market only, where no copyright issues emerged, and the other for export. Since the German Jesuit was then lecturing at Ingolstadt, printer Mascardi felt free to publish his letters in Italy, but north of the Alps, privileges might be infringed. Cinti 44; Stillman Drake, Galileo at Work (Chicago 1978), 198; Carli and Favaro 60; Cinti 44; Dawson 2587; Riccardi I, 509; Waller 12046.

Two text leaves following the two Jovian remargined plates (V3 & V4) very neatly reinforced at the inner (gutter) fold. Double-page engraving of sun spots entitled “Maculae in sole apparentes observatae,” one full-page text engraving and twenty-two text engravings, metalcuts and typographic diagrams. Bound in limp parchment, some spotting, foxing, generally crisp. 8 1/2 x 6 1/4 in. Binding firm. NO WRITINGS OR MARKINGS.

The full-page engraved portrait of Galileo is his first to be published in one of his books. A genuine rarity in highly collectible condition.