Bridgwater was developed during the Industrial Revolution as the area's leading port. The River Parrett was navigable by large ships as far as Bridgwater. Cargoes were then loaded onto smaller boats at Langport Quay, next to the Bridgwater Bridge, to be carried further up river to Langport; or they could turn off at Burrowbridge and then travel via the River Tone to Taunton. The Parrett is now only navigable as far as Dunball Wharf. Bridgwater, in the 19th and 20th centuries, was a centre for the manufacture of bricks and clay roof tiles, and later cellophane, but those industries have now stopped. With its good links to the motorway system, Bridgwater has developed as a distribution hub for companies such as Argos, Toolstation, Morrisons and Gerber Juice. AgustaWestland manufactures helicopters in Yeovil, and Normalair Garratt, builder of aircraft oxygen systems, is also based in the town. Many towns have encouraged small-scale light industries, such as Crewkerne's Ariel Motor Company, one of the UK's smallest car manufacturers.