The line is from Gilbert and Sullivan's 'Iolanthe'. It comes from a song of the Lord Chancellor who is describing a nightmare. It is sung feverishly, as though in panic:
" For you dream
You are crossing the Channel and tossing about in a steamer from Harwich
Which is something between a large bathing machine
And a very small second-class carriage"
Harwich is fairly 'south' itself. It's in the South East, on the coast of Essex ;)