The Galileo Manuscript
Draft of a letter to Leonardo Donato, Doge of Venice, circa August, 1609.
In a 1597 letter to Johannes Kepler, Galileo wrote that he had come to agree with Copernicus many years before. He continued, however, to teach the celestial sphere and the Ptolemaic system in his academic lectures at the University of Padua. In 1609 he received a description of a telescope which had been developed the year before in the Dutch town of Middelburg by an optician, one Jan Lippershey. Applying his knowledge of optical science, Galileo built such a glass or telescope for himself, and in the draft letter shown above offers his new "occhiale" to the Doge of Venice for use in warfare. The final letter, revised from this draft, was sent on August 24, 1609. It is in the State Archives in Venice.
The lower part of this sheet shows the use to which Galileo put this optical device: as he viewed the skies on successive evenings in January, 1610, he noted his first observations of the planet Jupiter and four of Jupiter's moons.
Most Serene Prince.
Galileo Galilei most humbly prostrates himself before Your Highness, watching carefully, and with all spirit of willingness, not only to satisfy what concerns the reading of mathematics in the study of Padua, but to write of having decided to present to Your Highness a telescope that will be a great help in maritime and land enterprises. I assure you I shall keep this new invention a great secret and show it only to Your Highness. The telescope was made for the most accurate study of distances. This telescope has the advantage of discovering the ships of the enemy two hours before they can be seen with the natural vision and to distinguish the number and quality of the ships and to judge their strength and be ready to chase them, to fight them, or to flee from them; or, in the open country to see all details and to distinguish every movement and preparation."
[Below the text are diagrams and notes explaining the position of Jupiter on several nights.]
Gift of Tracy W. McGregor, 1938.
Last modified: 11/18/2010
tag this page
