In Gemma Frisius, an eminent professor of mathematics in the University of Louvain, and at one time a pupil of Apianus, he appears, as before noted, to have found a sympathetic friend and counselor.[263] It probably was Frisius who suggested a career for the young scientist, since we find him, shortly after graduation, turning his attention to the manufacture of mathematical instruments, to the drawing, engraving, and coloring of maps and charts, wherein he found a vocation for the remainder of his life. In 1537 his first publication, a map of Palestine, appeared, to which he gave the title “Amplissima Terrae Sanctae descriptio.”[264] Immediately thereafter, at the instance of a certain Flemish merchant, he undertook the preparation of a map of Flanders, making for the same extensive original surveys. This map was issued in the year 1540.[265] Mercator’s first published map of the world bears the date 1538. This map was drawn in the double cordiform projection which seems first to have been employed by Orontius Finaeus in his world map of 1531.[266] In this map Mercator departed from the geographical notions generally entertained at this particular period which made America an extension of Asia. He represented the continent of Asia separated from the continent of America by a narrow sea, an idea which increased in favor with geographers and cartographers long before actual discovery proved this to be a fact. This map is one to which great importance attaches, but it is not the first world map on which there was an attempt to fasten the name America upon both the northern and the southern continents of the New World, although it frequently has been referred to as such; this honor, so far as we at present know, belongs to a globe map referred to and briefly described above.[267] His large map of Europe, the draughting of which appears to have claimed much of his time for a number of years, was published in the year 1554, and contributed greatly to his fame as a cartographer.[268] In 1564 appeared his large map of England,[269] and in the same year his map of Lorraine based upon his own original surveys.[270] In the year 1569 a master work was issued, this being his nautical chart, “ad usum navigantium,” as he said of it, based upon a new projection which he had invented.[271] It is the original chart setting forth the Mercator projection which is now so extensively employed in map making. In the year 1578 he issued his revised edition of the so-called Ptolemy maps, and eight years later these same maps again, revised with the complete text of Ptolemy’s work on geography. Mercator expressly stated it to be his purpose, in this last work, not to revise the text in order to make it conform to the most recent discoveries and geographical ideas, but the rather to have a text conforming, as nearly as possible, to Ptolemy’s original work. This edition still ranks as one of the best which has ever been issued. His great work, usually referred to as his