interpolate.target = function(_) {
      var cx1 = Math.cos(x1 = _[0] * d3_geo_radians), sx1 = Math.sin(x1);
      cy1 = Math.cos(y1 = _[1] * d3_geo_radians);
      sy1 = Math.sin(y1);
      kx1 = cy1 * cx1;