Note 23 — Extract from the Preface of Kepler’s Dioptrics. Augsburg, 1611.

The text of the four letters of Galileo followed here is that given in the edition of Galileo’s works published at Florence, 1842-56; that in the edition of Kepler’s Dioptrics, published at Augsburg, 1611, is very inaccurate. These letters were written to Giuliano de’ Medici, ambassador of the Grand-Duke of Tuscany to the Emperor Rudolf II. at Prague.