Most Serene Prince: Galileo Galilei, your Serenity’s most humble servant, labouring assiduously and with all his heart not only to do his duty as lecturer on mathematics in the University of Padua, but also to bring your Serenity some extraordinary advantage by means of some useful and signal discovery, now appears before you with a new device of eyeglass, the result of the most recondite theories of perspective; the which [invention] brings objects to be visible so near the eye and shows them so large and distinct, that what is distant, for instance, nine miles, seems as if it were only one mile away, a fact which may be of inestimable service for every business and enterprise by land and sea; for it is thus possible, at sea, to discover the enemy’s vessels and sails at a far greater distance than is customary, so that we can see him two hours and more before he can see us, and by distinguishing the number and nature of his vessels, we can judge of his forces and prepare for a pursuit, or a battle, or for flight. In the same manner, on land, the quarters and the defences of the enemy within a strong place can be descried from an eminence, even if far away; and even in the open country, it is possible with great advantage to make out every movement and preparation; moreover, every judicious person will clearly perceive many uses [for the telescope]. Therefore, deeming it worthy to be received and considered very useful by your Serenity, he [Galileo] has determined to present it to you, and to leave it to your judgment to determine and provide concerning this invention, in order that, as may seem best to your prudence, others should or should not be constructed. And this the aforesaid Galilei presents to your Serenity as one of the fruits of the science which he has now professed in the University of Padua during more than seventeen years, trusting that he is on the eve of offering you still greater things, if it please the Lord God and your Serenity that he, as he desires, may spend the rest of his life in the service of your Serenity, before whom he humbly bows, praying the Divine Majesty to grant you the fulness of all happiness. The letter is not dated, but on the twenty-fifth of August 1609 the Signory appointed the astronomer professor for life, with ‘three times the highest pay ever granted to any lecturer on mathematics.’ It was in Padua that Galileo invented the microscope, observed the moon’s surface, and the spots on the sun, discovered that the milky way and the nebulæ consist of many small fixed stars, discovered Jupiter’s moons, Saturn’s rings, and the fact that Venus revolves round the sun, ‘and not below it, as Ptolemy believed.’ Much has been written of late about Galileo, but most of what has appeared seems to be founded on this life by his pupil Viviani.