CONTOUR, CONTOUR LINE, a line drawn upon a map through all the points upon the surface represented that are of equal height above sea-level. The word is French and means gen erally "outline," from the Med. Lat. contornare, to round off. The points mentioned lie upon a horizontal plane at a given eleva tion passing through the land shown on the map, and the contour line is the intersection of that horizontal plane with the surface of the ground. The contour line of 0, or dcrtum level, is the coastal boundary of any land form. If the sea be imagined as ris ing iooft. a new coastline with bays and estuaries indented in the valleys would appear at the new sea-level. If the sea sank again to its former level the oof t. contour would be represented by the beach mark made when the sea was iooft. higher. If instead of receding the sea rose continuously at ooft. per day a series of levels ooft. above one another would be marked daily upon the land until at last the highest mountain peaks appeared as islands less than ooft. high. A record of this series of advances marked , upon a flat map of the original country would give a series of contour lines at iooft. intervals. Contour lines of this character, at varying intervals according to the scale of the map, are marked on most maps that indicate topographical features.