The Thames and Severn Canal was authorised by an Act of Parliament on 17 April 1783 but details of the tunnel had not been worked out, and arguments about its size continued for two to three months. Regular barges on the Severn were trows which were wide; those on the Thames were Thames barges, wide. The only long tunnel in the country at the time was Harecastle Tunnel, suitable for narrow boats just wide. A party of Commissioners from the Thames thought that the cost of a wide tunnel would be prohibitive, and that it should be built for narrow-beam boats, with the trows or barges unloading their cargos at each end of the tunnel.