Stevin, Mathematician to Prince Maurice of Nassau, had by his orders composed a small treatise for the instruction of pilots in finding a ship's place at sea. He formed a table of the variations of the needle, according to the observations of Plancius, a famous geographer, and added directions how to use it. Grotius translated into Latin this work, which he could not have understood without knowing the Mathematics, and particularly Mechanics; Statics, and the art of working a ship, and of finding her place at sea, being branches of that science. This translation he dedicated to the Republic of Venice by a letter dated April 1, 1599; in which he says, that having been in France about a year before, with the Ambassadors of the States, he there saw Signior Contarini, Ambassador of Venice; that a comparison happening to be made in conversation between the Republics of Holland and Venice, he immediately resolved to dedicate to the Venetians the first work he published that might be agreeable, or worthy to be presented to them; that an opportunity now offer'd of fulfilling this resolution, and that he dedicated to them the translation of Stevin's work because Prince Maurice had recommended it to the colleges of the Admiralty to be studied by all officers of the Navy; and as the Republic of Venice attentively cultivated Navigation, this book might be as useful to her as to Holland. XII. The year following, that is to say, 1600, Grotius published the Treatise which Aratus, of Sola in Cilicia, composed in Greek on Astronomy, two hundred and some odd years before the birth of Christ. It is known by the name or the _Phaenomena of Aratus_. The title fully shews what Grotius gives in this book. It contains the Phaenomena of Aratus in Greek with Cicero's Latin interpretation, the places where Cicero's Translation is wanting being supplied; a Translation of the same Phaenomena, ascribed to Germanicus; the fragment of Aratus's Prognostics, and the forms of the constellations as found in a Manuscript; with Remarks upon the whole, the Paraphrase of Festus Avienus, and marginal notes. This work is dedicated to the States of Holland and West Friesland: the author in the dedication promises them others more considerable. The book is a prodigy of science and erudition: it discovers a great knowledge of Physics, and especially of Astronomy. The Latin verses made by Grotius to supply those of Cicero that were lost, are not inferior to the lines of that great man, in the opinion of the Abbe d'Olivet, an excellent judge, who likewise thinks the supplement a very good commentary on Aratus's work. The corrections made by Grotius in the Greek are most judicious; and his notes shew he had read several of the Rabbi's, and had some tincture of the Arabic.