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Primary sourceBookOctober 1623

The Assayer

Galileo Galilei · October 1623

Galileo's 1623 polemical book arguing that nature must be studied through mathematics, written during his dispute with the Jesuit Grassi over comets.

Galileo wrote this book, a milestone work laying out his vision of mathematics as the language of nature.

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Title page of Il Saggiatore, Rome 1623, in an ornate engraved architectural frame with two allegorical female figures, Filosofia Naturale and Matematica, and a central text block naming Galileo Galilei. Handwritten annotations and library stamps appear on the page.
Galileo Galilei, Il Saggiatore (The Assayer), title page, Rome, 1623.

About this source

What it is

The Assayer (Il Saggiatore) is a book written by Galileo Galilei, published in Rome in October 1623. The title page shows the crest of the Barberini family, since the book was dedicated to the new pope, Urban VIII, formerly Cardinal Maffeo Barberini, a supporter of Galileo.

Why it matters

The book grew out of a public dispute between Galileo and the Jesuit astronomer Orazio Grassi (writing as

This book is part of the curated material that grounds the AI version of Galileo Galilei on Humy.ai — when students ask about related events, the AI can quote it and cite it.

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Title page of the 1610 Latin book Sidereus Nuncius by Galileo Galilei, printed in Venice by Thomas Baglionus. Black text in several type styles, with a central woodcut emblem of a seated figure in an oval frame flanked by cherubs. Handwritten shelfmark appears at the bottom.Book

Primary source

Sidereus Nuncius

Galileo Galilei · 1610

Engraved oval portrait print of a bearded older man with receding hair, wearing a white collar and a buttoned dark coat, in an oval frame. Inscribed 'Galileus Galileus Florentinus' at top, 'Eques Octavius Leonus' and 'Romanus pictor fecit' at bottom, and dated '16 24' with 'Superiorum licentia'. Printed on cream paper with a grayscale color scale at right.Painting

Primary source

Portrait of Galileo Galilei (1624 print)

1624

Oil portrait of an elderly bearded man with a white collar, wearing a black robe, seated at a table with books, a pair of dividers in his raised hand, and a celestial globe to the left, in a dark background. A brass plaque on the frame reads Galileo Galilei.Painting

Primary source

Oil Portrait of Galileo in His Study

Unknown Italian painter · 18th century (?)

Oval-framed line engraving of an older bearded man in a large white collar and dark doublet, with a Latin inscription above reading Galileus Galileus Florentinus, and an artist credit below. Handwritten Italian caption on mount beneath.Painting

Primary source

Galileo Galilei, line engraving by Ottavio Leoni

Ottavio Leoni · 1624

Title page of the 1632 Florentine edition of Galileo Galilei's Dialogo, printed in large serif capitals with a decorative woodcut emblem, imprint 'In Fiorenza, Per Gio: Batista Landini MDCXXXII', and several library stamps and handwritten shelf marks.Book

Primary source

Dialogue Concerning the Two Chief World Systems

Galileo Galilei · 1632

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