Do something new everyday

That's what they say you should do to help slow down time. And I think I agree. Today, I walked along part of the 'Innocent Railway' cycle track from Duddingston up to St Leonards, including going through the tunnel that goes under the top end of Holyrood Park.
The public information plaque states
"You are standing on one of Scotland's pioneering Railways. The Edinburgh and Dalkeith Railway was nicknamed "The Innocent Railway" because it was originally horse-drawn in an age which thought steam engines dangerous. It was built to transport coal from the Dalkeith area to Auld Reekie. To the surprise of the promoters, however, the public rapidly took to this convenient novelty and soon 300,000 passengers were carried annually.
Thereafter, passengers became as important as freight to the railways. Open carriages, wagons and converted stagecoaches were the first rolling stock. Among its engineering features were an early tunnel, a cast iron beam bridge and an outstanding timber viaduct on masonry piers. The first two still survive. The viaduct at Thornybank, Dalkeith was finally demolished in the 1960s."

It opened it July 1831 and the success of the line meant that it cost the North British Railway Company £113,000 in 1845. For anyone who has ever played the '18xx railway boardgames' this will be a familiar pattern, as small private companies were bought up by larger ones.