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406 authority on the subject adds, dates from his time. He seems to have had a strong natural taste for the study of this science, to which he himself testified when he said, in the preface to his "Chronology": "I consecrate myself wholly to that study, so beautiful, so useful, and at the same time so difficult. Nothing in the world is so pleasant to me. In fact, compared with it, other occupations, no matter how necessary they may be, are irksome to me." In his opinion, a knowledge of geography was indispensable to successful government and lucrative commerce. "Without maps, giving visible representations of the whole of an empire and its different countries," he said, "merchants would not be able to reach the richest and most important lands, to trade there, and bring all the earth into fraternity with Europe; and, without them, princes could only with difficulty and by means of intermediaries, often of doubtful fidelity, arrive at safe and stable decisions respecting the government of their dominions." Thus, availing himself of the instructions he had received from Gemma le Frison, and having served no other apprenticeship in the art, he began, about 1537, to design on paper, and then to engrave on copper, and illuminate the chorography of various countries. "The skillful instrument-maker became also in a short time an accomplished map-engraver; and no maps of his time were comparable in workmanship with his."

Mercator's principal title to fame rests upon his invention of the method of drawing maps, which is known as Mercator's Projection. Under this system the map represents the earth as an unrolled cylinder, and the poles are remanded to infinity. The parallels of latitude and the meridians are drawn as straight lines, crossing one another at right angles. This method gives a tolerably fair representation, and accurate enough for practical purposes in the neighborhood of the equator and for about thirty degrees on either side of it; but, in approaching the poles, the proportions of the parts are distorted. The length of the degrees of longitude and of the parallels is exaggerated—vastly in the immediate neighborhood of the pole—for to preserve the parallelism of the meridians and their perpendicularity to the parallels of latitude, the degrees must be drawn of equal length in all parts of the map. The plan has, however, the great practical advantage for sailors of causing the curve drawn on the sphere crossing all the meridians at the same angle—the loxodromatic curve, which a vessel would describe in sailing around the earth without changing its course—to be projected into a straight line. It thus furnishes a way in which the bearing of a vessel sailing directly between two distant ports can be clearly discerned on the map. While Mercator was successful in executing the designs of his maps on this method, he was not able to explain its theory, or at least did not explain it. The explanation was given by Edward Wright, in 1599, in his "Correction of Errors in Navigation," and from this circumstance the method was long known to the English as Wright's Projection.