This journey goes up the west coast of Scotland from Ayr to Skye Ep24. Roybridge to Glenfinnan. Michael investigates one of the great geological mysteries of the 19th Century, the parallel roads of Glenroy. Plus, he finds out how the Victorians put a weather observatory on the top of Ben Nevis and takes a steam train across one of the most spectacular viaducts in Britain at Glenfinnan.