# File lib/geo_ruby/simple_features/envelope.rb, line 16
      def extend!(envelope)
        lower_corner.x = [lower_corner.x,envelope.lower_corner.x].min
        lower_corner.y = [lower_corner.y,envelope.lower_corner.y].min
        upper_corner.x = [upper_corner.x,envelope.upper_corner.x].max
        upper_corner.y = [upper_corner.y,envelope.upper_corner.y].max
        self
      end