# Page:1902 Encyclopædia Britannica - Volume 26 - AUS-CHI.pdf/760

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the idea of representing the earth’s surface on a cylinder, in which the length of the degrees of latitude were increased as they approached the pole in the same proportion as those of longitude decreased on the globe. This idea was perfected about 1590 by Edward Wright, an Englishman, and it is on his principle that the present charts are drawn on what is known as “ Mercator’s proMercator’s jection.” The advantage of this projection to projec . saiior js that the ship’s course between any two places is represented by a straight line. On a sphere the meridians all converge towards the pole, the degrees of latitude are equal, those of longitude decreasing towards the pole; on a Mercator’s chart the meridians are drawn as parallel lines, and the degrees of longitude are all equal. To compensate for this error, the degrees on the Mercator chart are increased as they approach the pole beyond their actual lengths, in the same proportion as the degrees of longitude on the sphere diminish in length as they approach the pole. The length of a degree of latitude in the parallel of 70° is consequently three times that of a degree at the equator. It is, however, only when equatorial and polar regions are contrasted that the distortion becomes evident—contiguous countries and seas appear but little out of proportion to each other, and no other projection is known that so well meets nautical requirements. Distances on a Mercator chart are measured on the latitude scale, on the sides of the chart, taking care to use that part of the scale which is in the same latitude as the ship; e.g., distances between places within the parallels of 50° and 60° must be measured upon the latitude scale between 50° and 60°. The British Admiralty charts are compiled, drawn, and issued by the Hydrographic Office. This department of the Admiralty was established under Earl Spencer Hydropy an or(Jer in council in 1795, and consists of