A large gas jar is filled with water and a dye is added to make it visible. It acts as a cylindrical lens and focuses light into a line rather than a point. The lens compresses the image in the direction perpendicular to this line, and leaves it unaltered in the direction parallel to it (in the tangent plane). The person standing behind the jar, from the viewers point of view, appears as an upright but laterally compressed image and because the person is further away than the focal length of the lens the image is also inverted horizontally ( see model's fringe). The water is formed into a lens by the shape of the jar.