Certain of the great roads going north out of London continue far into the country a sort of attenuated and interrupted spectre of a street, with great gaps in the building, but preserving the line. Here will be a group of shops, followed by a fenced field or paddock, and then a famous public-house, and then perhaps a market garden or a nursery garden, and then one large private house, and then another field and another inn, and so on.