If one is taught to be critical in geometry and then is led to apply the same critical attitude consciously toward history and business, one will be far more likely to be critical in matters of politics than if this habit had been developed in connection with geometry alone. So, too, general principles learned from only a few typical facts ace less likely to be seen in new applications than if they have been discovered to apply to a great variety of cases. Here, then, is seen the most important use of correlation : It practices one in using his knowledge of facts and principles and his habits of work in connection with the greatest range of material. Thus we may be said to receive a really effective form of niental discipline. See Apperception, Teaching, Method op, and Modern Education. Consult Educational Psychology by Thorndike and The Educative Process by Bogley.

Mentone (mĕn~tō'nĕ), a French seaport, is on the- Mediterranean, near the borders of Italy, 14 miles from Nice. On the north and west spurs of the Alps, 3,000 or 4,000 feet high, shelter it from winter-storms. Consequently the climate is mild, making it a favorite winter-resort for invalids. It is surrounded by beautiful suburbs and by olive-groves and plantations of oranges and lemons. The trade of the region is largely in olive-oil, lemons, oranges and wine. At the eastern end of the bay are the bone-caves, about 88 feet above the Mediterranean, in which many curious remains are found, belonging to prehistoric times. Mentone belonged to Monaco until 1848, when the inhabitants put themselves under the protection of Sardinia. Twelve years later (1861) Sardinia ceded the town to France. Population about 10,000. See Bennet's Winter and Spring on the Shores of the Mediterranean.

Men'tor, the son of Alcimus, the friend of Ulysses, to whose care that hero intrusted his son Telemachus when setting out for the Trojan war. On account of the fidelity with which he discharged this trust, his name became a synonym for one chosen to be a guide or instructor of youth.

Mephistopheles (mcfts-tŏf-lz), in old legends a character representing the principle of evil or another name for the devil. The name is thought to be derived from the Hebrew, and means "one who loves not light." The character is best known from its appearance in Goethe's Faust.

Mercator (mr-k'tr), Qerard, a Flemish geographer of the 16th century, was born at Rupelmonde, Flanders, March 5, 1512, his real name being Kraemer, "merchant," of which Mercator is the Latinized form. He took his degree as bachelor of philosophy at Louvain, but devoted his later years to the study of geography. In 1559 he was appointed cosmographer to the duke of Cleves. He published several im-

portant works, including maps and descriptions of France, Germany and Great Britain. He did a great deal to put geographical science upon a secure footing and to popularize the researches of the learned. Some of his later works were of a religious character and were supposed to favor the Reformed doctrines. He died in Prussia, Dec. », 1594.

Merca'tor's Projection is that kind of map-making in which the meridians of longitude are drawn as if parallel, the circles of latitude being in consequence all at right angles with them. In order to lay down the sailing-course of a vessel, which in fact is a curve, so that it shall be represented as a straight line and the angle of the course be readily measured upon the chart, it is necessary to represent the surface of the earth as a plane instead of spherical. This requires, of course, that the degrees of longitude, which vanish at the poles, should be represented as the same length that they are at the equator. In order to draw a chart upon which all sailing-courses may be represented by straight lines, sea-maps are constructed according to the scale devised by Mercator, the distances as we go toward the pole being immensely exaggerated. The amounts of these exaggerations are taken from a table of meridional parts. Given then the starting point of a ship and its meridian and latitude at the close of the day, a straight line between these two points found upon a Mercator's chart would indicate its course, and lines drawn parallel with the meridian passing through the termination and one parallel with the latitude of the starting point would at their junction form a right angle. The angle of the course sailed would be found by measuring the angle at the base.

Merchant-Marine. The United States merchant-marine, or body of commercial shipping, affords a strange contrast to other American industrial concerns in that, while other industries have rapidly and steadily developed, the merchant-marine has no less rapidly and steadily declined. In early colonial days American shipping was a serious competitor with the English merchant-marine. The navigation acts, which date from 1645, prohibited importation into the colonies in other than English or colonial-built ships, and thus rather favored the shipbuilding industry in America. The ascendency of the American merchant-marine was still in evidence during and after the Revolution. The earlier wars of the French Revolution left the carrying-trade chiefly in the hands of American merchants; and between 1789 and 1798 the registered tonnage of American shipping was augmented 384 per cent. The maximum tonnage was reached in 1861 with a registration of 496,000 tons. The introduction