4 o6 THE POPULAR SCIENCE MONTHLY. 



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 inter- 

 mediaries, often of doubtful fidelity, arrive at safe and stable decisions 

 respecting the government of their dominions." Thus, availing him- 

 self 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 cylin- 

 der, 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 ap- 

 proaching 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 advan- 

 tage for sailors of causing the curve drawn on the sphere crossing all 

 the meridians at the same angle the loxodromatic curve, which a ves- 

 sel 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 suc- 

 cessful 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 ex- 

 planation 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. 



