d3.geo.mercator = function() {

  var scale = 500,

      translate = [480, 250];

  function mercator(coordinates) {

    var x = coordinates[0] / 360,

        y = -(Math.log(Math.tan(Math.PI / 4 + coordinates[1] * d3_geo_radians / 2)) / d3_geo_radians) / 360;

    return [

      scale * x + translate[0],

      scale * Math.max(-.5, Math.min(.5, y)) + translate[1]

    ];

  }

  mercator.invert = function(coordinates) {

    var x = (coordinates[0] - translate[0]) / scale,

        y = (coordinates[1] - translate[1]) / scale;

    return [

      360 * x,

      2 * Math.atan(Math.exp(-360 * y * d3_geo_radians)) / d3_geo_radians - 90

    ];

  };

  mercator.scale = function(x) {

    if (!arguments.length) return scale;

    scale = +x;

    return mercator;

  };

  mercator.translate = function(x) {

    if (!arguments.length) return translate;

    translate = [+x[0], +x[1]];

    return mercator;

  };

  return mercator;

};