Henry Bell had become interested in steam-propelled boats, and corresponded with Robert Fulton to learn from the Charlotte Dundas venture. In the winter of 1811/1812 he got John and Charles Wood of John Wood and Company, shipbuilders of Port Glasgow, to build a paddle steamer which was named the Comet after the "Great Comet" of 1811. The 28 ton craft was long and broad. It had two paddle wheels on each side, driven by engines rated at : at a later date the twin paddlewheels were replaced by a single paddlewheel on each side. The two engines were made by John Robertson of Glasgow, and the boiler by David Napier, Camlachlie, Glasgow: a story has it that they were evolved from an experimental little steam engine which Bell installed to pump sea water into the Helensburgh Baths. The funnel was tall and thin, and a yardarm allowed it to support a sail when there was a following wind. A tiny cabin aft had wooden seats and a table. Comet was launched on 24 July 1812 with her trial run on6 August from Port Glasgow to the Broomielaw in Glasgow, taking three and a half hours for the. On 15 August 1812, Bell advertised in a local newspaper "The Greenock Advertiser", that the Comet would begin a regular passenger service from that day, a distance of each way: On 15 August Comet made the first commercial sailing from Glasgow for Bowling, Helensburgh and Greenock, opening the era of the steamboat on the Clyde, and more widely in Britain and Europe. The fare was "four shillings for the best cabin, and three shillings for the second." As the vessel clearly had no cabins in the modern sense it is unclear what this meant.
The success of this service quickly inspired competition, with services down the Firth of Clyde and the sea lochs to Largs, Rothesay, Campbeltown and Inveraray within four years, and the Comet was outclassed by newer steamers. Bell briefly tried a service on the Firth of Forth.
James Watt – by this date Bell offered a return trip from Glasgow to Rothesay on the same day which Watt undertook
Wreck
Bell had the Comet lengthened and re-engined, and from September 1819 ran a service to Oban and Fort William, a trip which took four days. On 15 December 1820 the Comet was wrecked in strong currents at Craignish Point near Oban, with Bell on board. No lives were lost. One of the engines ended its working days in a Greenock brewery, and is now in The Science Museum in London.
''Comet II''
Bell built another vessel, Comet II, but on 21 October 1825 she collided with the steamer Ayr off Kempock Point, Gourock, Scotland. Comet II sank very quickly, killing 62 of the estimated 80 passengers on board, including the son-in-law of John Anderson, a friend of Robert Burns. Also drowned were recently married Captain Wemyss Erskine Sutherland of the 33rd Regiment and Sarah née Duff of Muirtown. After the loss of his second ship, Bell abandoned his work on steam navigation.
Replica
A replica of the Comet made by shipyard apprentices now stands prominently in Port Glasgow.
