Back online again! So, firstly, why is it dangerous to have a nap in a railway carriage?
Too easy? Then how about this one?
Secondly, what is the difference between a person late for the train and a school-mistress?
1st: Because the train always runs over sleepers.
2nd: One misses the train, the other trains the misses.
Source: “A Thousand and One Riddles, With a Few Thrown in”, Victorian book published by George Routledge and Sons Limited, London.