Galileo had begun manufacturing his compasso in the 1590s and for ten or more years he sold the instrument together with a manuscript manual of instructions for its use prepared by his amanuensis. By 1606, the instrument had undergone several modifications, and the applications described in the manuscript instructions expanded from 12 to 32. The transition to print was guided both by reasons of economy and Galileo’s decision to assert his rights as inventor of the instrument. Although he was not much interested in the instrument, Cosimo accepted the book’s dedication.
Galileo claimed that only 60 copies were printed, stating in his preface to the reader “Et per tal causa ne hò fatte stampare appresso di me 60. copie sole, per presentarne insieme con lo Strumento con la somma diligenza”. Galileo’s letters prove that he did in fact present or sell his instrument accompanied by a copy of the Compasso. An uncertain number of copies were printed by Marinelli on a superior paper, marked “with a seven-spoked wheel, its inner hub made of two concentric circles” (Paul Needham, Galileo makes a book: the first edition of the Sidereus Nuncius Venice 1610, Berlin 2012, pp.30-31, citing the British Library copy as an example of the special-paper issue). The survival of some 25 copies suggests that the print run exceeded 60 copies. Nevertheless, the edition must have been soon exhausted, since in 1610 Galileo advised a correspondent that it was out of print (“non se ne trovando più copie”).
Sixteen institutional copies of the Compasso are known (Library of Congress, Washington D.C.; University of Illinois at Champaign-Urbana; University of Oklahoma; Beinecke Library, Yale; Huntington Library; Berlin State Library; British Library; Edinburgh University Library; Jagiellonian Library, Krakow; National Library, Florence; Austrian National Library; Museo Galileo, Florence; Marciana Library, Venice; Vatican Library; National and University Library, Ljubljana; Science Museum Library, Wroughton); in addition there are three or possibly four genuine privately owned copies.
Sotheby’s is grateful to Prof. Nick Wilding for confirming the authenticity of the present copy by direct examination in February 2018 and for the census of copies.
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