Devices for constructing such paraboloids are known as rotating furnaces. The foci of all these paraboloids are located at the origin. These include ellipsoids, cylinders, cones, paraboloids, and hyperboloids in all of their various forms. The wood hyperbolic paraboloids were destroyed in 1962 by the Columbus Day Storm. Join the paraboloids "y" = "xz" and "x" = "yz". They possess elliptic paraboloids as one-coordinate surfaces. The paraboloids were concrete shells, shaped like an inverted umbrella. Archimedes' investigation of paraboloids was probably an idealization of the shapes of ships' hulls. Quadric surfaces include ellipsoids (including the sphere), paraboloids, hyperboloids, cylinders, cones, and planes. The two paraboloids together look like a pair of orchids joined back-to-back. These other paraboloids only seem like obstacles due to the self-intersecting nature of the immersion. In the image the paraboloids are seen to intersect along the "z = 0" axis.