Mercator expressed a full appreciation of the importance of astronomy as connected with geography. That science was then cultivated largely in connection with astrology and was invoked in the solution of the most trivial questions. For this he had a profound contempt, while he believed in the significance of celestial phenomena and extolled the study of them. "The purposes for which the luminaries of the sky are created," he said, "are much higher than to assist in the predictions of the astrologers. Those lights exist to reveal to man the omnipotence, the majesty, and the divinity of his Creator, and not to be at the service of the vanity of the astrologers. They exist to mark the revolutions of the centuries; it is for this that they become obscured and are dissolved to announce the end of ages and proclaim judgment upon the world. It was thus that in the time of the passion of Christ, when the law was to be changed, Dionysius the Areopagite was permitted to see an eclipse. It was thus that Joshua perceived the astounding action of the hand of God in the spectacle of the sun. These bodies exist to mark the limits of days and years; and the stars, which glow by night in the firmament, shine upon the earth, and point out by their position the annual course of the sun." Mercator had collated the results of his studies on this subject, and had announced for publication a work embodying them, when death prevented his carrying out his intention.
Among the larger works mentioned by various authors as having been executed by Mercator, are the maps of Palestine, Flanders, Europe, Great Britain, Lorraine, the terrestrial and celestial globes already mentioned, and a great planisphere. These were all larger than the maps of the atlas. None of them, except the planisphere, are now known to be in existence. A few loose sheets from the plates of the atlas, preserved in collections at Brussels, London, the Hague, and St. Petersburg, constitute the chief part of the works of this class known to be by him that are now extant. For his chorography of Palestine—"Amplissima Terræ Sanctæ Descriptio" ("Most Ample Description of the Holy Land"), Mercator had to depend upon the best authorities he could command—"the testimony of an unknown traveler"—and they have not been identified. He is credited, however, with having made good use of the critical faculty in the composition of the work. It had the honor of having been sought for by the learned André Masius for the illustration of his commentary on the book of Joshua, who, in a letter to Georges Cassander, spoke of it in the most complimentary terms. The map of Flanders was produced after the spending of three years in personal surveys of the country, and appeared in 1540. It exists now only in reduced copies in the "Theatrum" of Ortelius and in Mercator's atlas; but the historian Jacques Marchantius, who had seen it, says that it surpassed all the maps of all other geographers. The map of Lorraine was also made after personal surveys, in the prosecution of which the author appears to have been exposed to
