A funnel is the smokestack or chimney on a ship used to expel boiler steam and smoke or engine exhaust. They are also commonly referred to as stacks. Purpose The primary purpose of a ship's funnel(s) is to lift the exhaust gases clear of the deck, in order not to foul the ship's structure or decks, and to avoid impairing the ability of the crew to carry out their duties. In steam ships the funnels also served to help induce a convection draught through the boilers. Design Since the introduction of steam-power to ships in the 19th century, the funnel has been a distinctive feature of the silhouette of a vessel, and used for recognition purposes. Funnel area The required funnel cross-sectional area is determined by the volume of exhaust gases produced by the propulsion plant. Often this area is too great for a single funnel. Early steam vessels needed multiple funnels ( had 5 when launched), but as efficiency increased new machinery needed fewer funnels. Merchant ships Merchant shipping companies (and particularly liner companies such as Cunard Line and ferries such as Red Funnel) were quick to recognise the publicity value of distinctive funnels, both in terms of shape, number of funnels, and the colours they were painted. In an era when ship hulls were uniformly painted black (to conceal inevitable dirt when loading the ship with coal) and superstructures were white (to control the temperature in the passenger accommodation in hot summers) the funnel was one of the few parts of the ship that a company could use to clearly differentiate its ships from those of its competitors. Each company would have their own "house colours", which were often used in publicity material as well as for recognition, making funnel colours an early form of trademark. Some companies became so closely associated with their funnel colours that their nickname became a de facto company name. For example, the shipping line actually registered as 'Alfred Holt & Company' was more widely known as the Blue Funnel Line. The Southampton, Isle of Wight and South of England Royal Mail Steam Packet Company has traded under the name Red Funnel for most of its 150+ year history. Other colours such as the red with black stripes of the Cunard Line and the all buff colour of P&O remain icons of their respective lines and have remained in use for over a