To a realist a hansom-cab driver is a man who makes twenty-five shillings a week, lives in a back street in Pimlico, has a wife who drinks and children who grow up with an alcoholic taint; the realist will compare his lot with other cab-drivers, and find what part of his life is the product of the cab-driving environment, and on that basis he will write his book.

To Stevenson and to the romanticist generally, a hansom cab-driver is a mystery behind whose apparent commonplaceness lie magic possibilities beyond all telling; not one but may be the agent of the Prince of Bohemia, ready to drive you off to some mad and magic adventure in a street which is just as commonplace to the outward eye as the cab-driver himself, but which implicates by its very deceitful commonness whole volumes of romance.

The novel-reader to whom _Demos_ was the repetition of what he had seen and known, and what had planted sickness in his soul, found the _New Arabian Nights_ a refreshing miracle.

Stevenson had discovered that modern London had its possibilities of romance.

To these two elements of his romantic equipment must be added a third--travel.
Defoe never left England, and other early romanticists less gifted with invention than he wrote from the mind's eye and from books.