I’ve listened to Innes Watson performing (on his own or supporting others) several times at the Islay Sessions. Here’s some beautiful music to wake you up this Saturday morning:
A quick search helped me to find out this was the Bennie Railplane. It of course reminds a bit of the famous Wuppertal Schwebebahn. While sadly it wasn’t a success and almost nothing physical remains of it today there are at least three videos of it in action, first from the National Library of Scotland: