Exercise 1: sample answer

Three degrees at 4 minutes per degree is 12 minutes, so Edinburgh's solar time was about 12 minutes behind Greenwich Mean Time (the true figure is a little over 12 minutes; check).

For railways this meant a train timetabled on London time would arrive at an Edinburgh station by an Edinburgh clock about twelve minutes "early" compared with the local public clocks. Station staff, passengers and connecting services would all be working to different times, so a single agreed time was needed to publish a reliable timetable and to run single-track lines safely.