the piers and the fast-flowing tides made the Queensferry crossing unsuitable for steamboats, but a paddle steamboat named the Queen Margaret was entered service in 1821 to tow sailing boats. Only the southern landing at Longcraig Pier could accommodate it, and because of the protruding paddles it could not load wheeled cargo. In that same year a fleet of sailing boats was introduced, but despite the efficiency of the operation, it could not compete with the Broad Ferry and in 1828 the Trustees consulted with engineer Thomas Telford with a view to making improvements. Tunnelling Coal workings George Bruce of Carnock tunnelled far out under the Forth in the 1600s, with John Taylor describing the pit in 1618. Taylor describes how after building a circular stone cofferdam, the workmen dug down into the coal seam, and followed it out to sea. In "eight and twenty or nine and twenty yeeres", they dug over an English mile out to sea. The tunnel was cut like an arch, and tall enough for a man to walk upright in most places, with three horses powering 36 buckets to keep the mine drained. The tunnel lasted until 1625, when the sea washed over the cofferdam in a storm. While this tunnel was never intended to be a means of transport, they are testimony to Bruce's "great knowledge and skill in machinery." A tunnel linking Valleyfield colliery in Fife to Kinneil colliery near Bo'ness was completed in 1964 so that coal could be transported under the Forth to the more modern coal processing facilities at Kinneil. The collieries were closed in 1978 and 1983 and the tunnel was sealed off. Transport proposals A proposal to tunnel under the Forth from Inchgarvie was put forward in around 1790, but the difficulty of tunnelling through whinstone meant it was not taken seriously. The success of coal mining operations to the west of Queensferry meant that a proposal mooted in 1805 for a tunnel of Inchgarvie was taken much more seriously. Twin wide arches would be bored at a maximum depth of through what was thought to be freestone, with construction anticipated to cost over a four-year period. A revised scheme in 1806 moved the tunnel westward, away from Hopetoun House, after objections from the Earl of Hopetoun. This scheme also received support, and Robert Bald suggested making soundings and borings as an initial step towards construction, but